Reasons to abandon single speed riding (in no particular order):
-30 gear drivetrains. I'm sorry, they cost how much? Whatever, your knees will cost more to replace than that, and at any rate the maintenance can't be all that bad. Can it? 50 miles of variable winds make gears seem almost necessary.
-The whole SS thing was a fad.
-As a cyclist, you profess to like all types of riding, but on your SS you're not at the crest of the wave anymore; its glory has passed. To those who are cyclists, it is now obvious that you are completely ex-post-fashion and definitely the wanker they suspected you of being all along, only moreso. To non-cyclists you always looked like a wanker anyway. Better to cut your losses.
-Gears on mountain bikes let you get up and over more stuff because you have leverage. It's nice to know that 28 tooth is there when you need it. And as for road, well who wants to ride a century on a SS? Remember how often when riding your SS you bitched under your breath (or maybe not so under your breath) that you needed something just a bit easier?
-Every hipster riding around town has 3 main accoutrements to show off his/her uber-hipster stylings:
1) at least one visible tattoo, likely on the theme of mis-interpretted chinese characters ("someone told me this means 'strength'". It doesn't.); 2) excitingly retro glasses, more than likely bought at a fancy shop specializing in rummaging through relatives' basements for old junk then selling this junk at high mark-up in same shop; 3) a single speed bike, often times a fixed gear.
-What were you thinking? Single speeds aren't easier. They weigh almost the same as your geared bike, and cost almost as much to set up.
-You just want to ride, man. It's too much to think about.
Reasons to abandon riding geared bikes:
-30 gears? What's the point? Geared right, and properly fitted to your bike, you're not going to blow out your knees. Geared bikes have tons of weight-adding, pointless gear overlap, and anyway who has the patience for fiddling with that stuff every 100 miles?
-Sick of all this trend-heavy technology. Geared bikes are based on trickle-down race technology and therefore are far more faddish than SSs ever were. Simplicity, man.
-As a cyclist, you profess to like all types of riding, but at least on a SS you are not a slave to the fancies of fast changing technologies and non-standardized component compatibility (um...). On a single speed you look to 'cyclists' like a 'cyclist' ...until they get close to you, and to non-cyclists you look (at least you think) like a normal person just out riding your bike. Except for your shoes. Not much you can do about that.
-Everyone rode fixed gears once, even in The Tour. You need something you can take downtown and not worry about getting ripped off, and that you can crash more than once before being denied warranty. Offroad, you can rip the rollers faster on a SS because they teach you how to pick a line better and how to maintain momentum. Remember how often when riding your geared bike you bitched under your breath (insert clever rejoinder here) because your derailleur couldn't find the gear you needed when you needed it?
-You'd rather get lumped in with the hipsters than look like one of those fools who think that if they dress like Lance they'll ride like him too. Overpriced retro glasses still look better than one of those logo-festooned 'kits'.
-What were you thinking? Geared bikes aren't easier! They weigh almost the same thing as your SS and cost a bit more to set up.
-You just want to ride, man. It's too much to think about.
-----