Personally it never did.
My Raleigh Record Sprint I bought for touring and fast blasts at the weekend, initially I never used it for commuting (I lived in house) but did so when I moved out of the staff accomm. I only ever fitted a rack and no mudguards, I liked the black stripe up my back
Sold that in summer 2002 (after 12 good years) and bought a Ridgeback Genesis Day 02, though I lusted over the Day 03 that had Dura Ace fitted! It promised road bike handling/geometry and also had the rack/guard mounts I'd had on the Raleigh yet it was a flat bar.
it wasn't the commute that made me buy it I was just trying to replicate what the Raleigh offered me for touring/fast rides, commuting needs were very much fulfilled due to the other requirements, touring pretty much covers what you need for commuting plus more IMO. I wasn't particularly looking for a flat bar bike but going from 52/42 + 6 speed 13-24 (maybe 26T big??) the Ridgeback just seemed like a very good all round bike that looked great, was a decent price (circa 35% of new for a mint condition year old bike) and of course having 27 gears, more was better right?
It was one of the best balanced bikes I've ever had, run it with 23mm Vittoria rubino pros (so not commuter tyres as such) was comfortable despite the alu frame and forks and with a rack/guards was ace all year round. 50mph down the local dual carriageway was a cinch yet it could easily carry a heavy load (I was well over a 100kg myself).
After 7 years of absolutely caning the bike in all weathers I decided I'd get something else in same mould and I found a Specialized Globe Pro for sale locally that again was going for peanuts despite having 50 miles on the clock. Not quite as tight as the 02 in handling terms but almost as light and had slightly lower gears, something I noticed when giving it the beans which meant I sacrificed the top end - I can spin out on my local short 7% on the way to the shops.
Aside from adding guards to the Ridgeback and Spesh the commutes in themselves haven't shaped the bikes at all really, they just were picked on the basis that they worked well at what a bike should do anyway, handle well, have a good selection of gears that are easily operated, reasonably light, robust and can carry stuff.
'Commuter' and 'touring' bikes are just concocted phrases for what are in actuality what a normal ordinary everyday bike should be, a bike that can do everything. All other types should have a label as they are more specialised and have a somewhat perceived narrower use though indeed they in turn can be used for a multitude of uses they just may need to be modified more.
