I think you’re on the right track, Tamara.
Allow me to quote Robert Heinlein:
People have stopped asking me that question. I never have a boyfriend. Last time someone asked me why, I believe my answer when something like “Well, I’m overweight, short, intellectually intimidating, sarcastic, demanding, insecure and generally unpleasant to be around at times. Only a small percentage of the dateable population is willing to overlook all that for my boobs.”
Nobody’s asked since. Although at a recent family shindig, all the cousins and I realized this would be the last open-bar affair until someone gets married. As the oldest unmarried one, everyone turned to me immediately, then almost as one, they looked to the next cousin, because I’m obviously not getting married anytime soon.
I’m allowed to give up my love life as hopeless, but they’re not. 
I don’t let that stop me.
I get the question from my mother often. Well, actually, she asks when I’m going to get a girlfriend. She refuses to believe I don’t want a girlfriend.
I thought telling her I wanted a boyfriend not a girlfriend would stop her. It hasn’t.
My dad’s sister keeps on asking me this. Well, actually its more of a sort of “when are you getting married?” question. I keep on trying to convince her that I’m a lesbian, in the hope that that’ll shut her up. 
I repulse those whom I find attractive and attract those whom I find repulsive … It’s quite a talent.
Oh and I think a female who took a spite to me spread rumour that I’m gay (I’m not), that wouldn’t help much really would it?
All that and nice boobs too?
If I were single, I’d be asking…
…how are YOU doing?
I used to get the “Why don’t you have a girlfriend routine?”
I’m not sure why, but I don’t get it anymore. For some reason “I haven’t found the right person” seemed to work pretty well.
They: “Why don’t you have a xxxfriend?”
You: “High standards.”
pause
You: “Higher than yours anyway”
This works great if they have an xxxfriend. They run off and cry.
I’m NOT gay!
“Because I’m only allowed one pet, preferably housebroken, and quiet.”
hah! that’s a great answer…I may have to use this one some time, especially if it’s somebody I don’t like
“why don’t you have a boyfriend?”
“because I’m fucking your husband.”
God, all you evil people and no one went for that? People, you disappoint me sometimes
Oh yeah, into my personal thesarus this goes!
I don’t get asked “Why don’t you have a boyfriend?” … I get, “You still don’t have a boyfriend?!”
For what it’s worth the next question after you finally have kids is simply “When are you going to have another kid?” My entire church is convinced we should produce a little brother or sister for Rosie RIGHT NOW. She’s two, and frankly we’re not quite coping with her yet.
For a response, I usually go with “I really like being single.” It often evokes rather wistful expressions from my questioner as they fondly remember their single days. But in order to get that response, you have to use the word “single”. Even if the question is about why I don’t have a girlfriend as opposed to a wife, it works just fine.
As to why people ask it, I think there’s a hefty chunk of the population that just can’t imagine being truly happy without a girlfriend/boyfriend/what have you. Most of them don’t mean to be rude, they’re just genuinely baffled.
Maybe the OP should reply:
“But I have lots of boyfriends … you just don’t see them because I kick them out the door very early in the morning!”
Sometimes makes me wonder how prevelent co-dependency is in the culture at large.
I don’t think it’s a particularly rude question, so I am never particularly rude back.
Generally I say something along the lines of “Ah, you know how it is” and smile.
I was a bit flabbergasted at the cheek of a girl I was in primary school with though, when I ran into her last year, in my old home town.
This woman is 35, she has five children, aged 18 to 5, by five different men; three of whom she was married to, all of whom battered the living daylights out of her on a pretty regular basis - two of them ended up in prison for it - one of them for attempted murder. ( :eek: )
She had never worked a day in her life, never been out of the country and never lived in any other town, apart from the one she was born in.
She had, she told me proudly, been to London once.
I’m guessing it was to the Old Bailey for the trial.
She told me all that, nearly without drawing breath, then asked :
Her - So, curly chick - are you married? Ever been married?
Me - Er, no and no. (Still all but dumbstruck at her tale of woe)
Her - Aw, don’t worry, (Here she patted me on the forearm and I saw about 25 cigarette burn scars on her hand ad a very ugly up and down scar in the inside of her wrist) I’m sure you’ll find someone one day; you aren’t *that * ugly. And once you find him, you’ll be OK.
Pity and insults, in one fell swoop, if you don’t mind!
Mindboggling.
IMO the question isn’t rude because it is such personal information. I wouldn’t consider whether I’m single or not to be deeply personal information about me. It’s just the way it’s worded in the OP, which is indeed the way many people phrase it, that pisses me off.
“WHY do you NOT have a boyfriend?”
Surely the only answer can be “Why would I have a boyfriend?”
It’s not like it’s some kind of disease and I’m not to be pitied either. If some nice fella comes along who takes my fancy, fine, if not there’s other things I have to be doing.
And I’m willing to bet most people who replied to this post also have these well meaning nice friends with boyfriends who keep trying to “rescue” you from your single faith-worse-than-death by asking you to consider every boring guy who shows any interest whatsoever.
P.s. Draelin’s reply is fabulous.
I am frequently assaulted by people who are horrified by the fact that I am 39 and not married.
It used to hurt my feelings, but now I have a great many snappy comebacks.
I love you guys.