This is the big deal. I don’t care WHAT you bottle your beer in; if it sits in said bottle for 10 months, it’s going to be skunky.
Which is why I largely stick to local microbrews: I can walk into any old bar or even grocery store and pick up a Shiner Bock or Saint Arnold Brown Ale that was bottled 12 days ago and refrigerated continuously since.
I had a correspondence with a marketing vice-president from Lowenbrau
about how, no matter where I bought the beer, it was always skunky.
Instead of at very least giving me a line of bullshit about how he would look into their dating & delivery practices or saying anything to appease me, he basically told me I was f*cked in the head, that Lowenbrau was never skunky, that perhaps my palate was that of a neanderthal and I didn’t know what good beer was supposed to taste like which is why I thought their beer was bad, blah, blah, blah.
:mad: I couldn’t believe the attitude of this guy. I was already pissed at the stores that were selling this tripe, but this guy insults me on top of it?
I’ve NEVER drank Lowenbrau since, and at one time 80% of the beer I consumed was Lowenbrau. Seems to me after Miller lost the license to make it, it turned to shit. (strange, as I don’t like anything else Miller makes.)
[FRANK BOOTH] *HEINEKIN ! ? ! ? Fuck that’s shit! PABST BLUE RIBBON!!! * [/FRANK BOOTH]
I can’t believe I got to use that line!!!
Custom or tradition mostly. Or marketing may think the flint or green bottles display the beer better to the customer, or give it a better image.
And there is truth to Barbarian’s statement that producers would be hesitant to make a switch because some customers might come to expect that flavor in the beer.
And even though the OP has already been answered, it never hurts to give a link or two. 
On the other hand, a bottle-conditioned beer (naturally carbonated) is arguably at its best at about six months of age. It’s drinkable up to two years, but that is a bit weird - no good at all for lagers, and the ales taste decidedly different at two years. Not bad, not skunked, but different. The flavours get incredibly complex, too much so. I often imagine a hint of brandy or port wine in it.