I need to do it more, it’s so hard to find a style of clothing that fits flatteringly and comfortably that I tend to wear them past when they should be retired before the next time I find any I like.
And that is just the basics.
When i find something i like, shoes especially, i go back and buy more of the same style so that when they wear out, i have replacements. i hate shopping for clothes, so buying several pairs of the same jeans, and same style shirts in different colors is my thing. my kids think I’m crazy, but it definitely speeds up the “what should i wear today?” process, as well as minimizing shopping time. I’m not as bad as Jeff Golblum’s character in “the fly” (and many others that i can’t name) but close.
Exactly this.
I wouldn’t normally do it for fleeces, but I’ve done it for jeans and T-shirts. Middlebro, who wears fleeces a lot more than I do, has done it for them.
I’m fairly picky about some of the things I wear, and it’s often nearly impossible to find just what I like, in the right cut, in my size, with the right blend of fabrics, at a price I’m willing to pay. So when I do I tend to buy a few of them, either in the same color or different colors.
I pretty much only shop clearance and sale items for clothes so if find something that I like and fits damn straight I’m getting it in multiple colors.
If a garment fits me well and I have the option, I always buy it in different colors. I get excited because most clothes I try on don’t work with my shape. So I don’t think it’s weird at all.
It wouldn’t be distinctive if you did! 
As for my response to the OP: for most men who buy their own clothes, it’s S.O.P.
I usually buy 6 of the same shirts, and 6 of the same pants. People do know that I change my clothes, however. I am very clean.
I do this all the time with shirts. I find something that appears to be good quality and fits I will buy a half dozen of them in different colors.
I do this a lot when I find something I like, especially if it’s on sale. Just before the holidays, I bought the same sweater in black, pink, green, and blue.
All the time. My basic work attire is a dress shirt and a sweater vest. I have different colors of each and I just mix and match.
Why wouldn’t someone do that? Find something that’s comfortable and suited to your needs, buy several (different colors if one cares about variety, which my husband does not).
Ditto - this seems pretty common for men. For work, I’ve got 8 identical white dress shirts and they didn’t bat an eye when I had them made. My dress slacks are 2 styles in 4 colors/patterns. Actually, thinking about it, my shoes are the same design, one pair in brown, one in black.
They make nine colors of pants? You own nine pairs of pants that are all the same size?
The first time I heard about doing this for anything other than underwear, I was a teenager and making most of my own clothes. I read an article about Jackie Onassis that talked about her buying her favorite designer t-shirt in every color it was made in, and of course as someone with frugal parents who made me wear hand-me-downs until I started sewing, that sounded so decadent! Now, it just seems practical. I have several sweaters that I bought in multiples of black for work, and then bought them in different colors for real life, especially if there is a good sale. Underwear is a given for this. And I have a favorite long sundress that doubles as a nightgown that I currently own in four colors, and each time they bring it out in a new color I buy it again.
Once read an article about a family whose summer “uniform” for the family was white socks, navy blue shorts and white and blue t-shirts. Since everyone was about the same size in the One-Size-Fits all type of stuff they wore for their summers on the Cape, the mom just bought dozens of each item, and laundry was very simple…a basket for each item, and no one “owned” any of it, so they didn’t waste time sorting or folding…you just grabbed from the basket.
I have to admit that I thought it was strange to buy several in one size, but I realized that I have been doing it. The only distinctive item I have in multiples is two prairie type skirts in blue and purple. What I do have a lot of is black and gray layering t-shirts and tank tops that I wear under a lot of things. I have multiple black shirts that are identical since I wear them so often.
I would never buy identical shoes, though. The world of shoes is too fabulous and varied to waste time buying identicals! I will cop to similar, though since I’ve got an obscene number of cowboy boots.
If I find sports shirts on sale, I will take them in several agreeable colors.
I almost inevitably buy clothing styles I like in multiple colors. My blue jeans version of this, learned after hard experience, is to buy multiple pairs of a style I like.
I do it all the time. I have such a hard time finding clothes that fit well, so when I finally find a winner, I’ll go right back to the rack I got it from and pick out a couple of other colors to buy with it.
I don’t think I have duplicates in pants right now, but I do in T-shirts and other tops, and definitely in bras. I always buy bras as triplets when I find a style that works. Usually a white, a nude, and a black version.