For a good many of us, bottles would take up more space then kegs do.
Then there's not being able to drink bottle carbonated beer direct from the bottle (unless you like drinking the trub, or the style has you drink that).
You can bottle from keg/tap rather easily when you want to take just a few with you (a 6 or 12 pack). I've done it and continue to do it in fact.
My brew fridge takes up little space. It's a 10 cubic foot Whirlpool fridge (freezer top, which has all my hops in it). I have three taps through the door, and four 3 gallon kegs inside.
As for the cost aspect. My time is NOT cheap. I'd rather spend a fraction of the amount of time it takes to bottle a batch with kegging.
Also, I can transfer my finished beer from my fermenter/aging vessel into the serving kegs without moving them at all. Since I'm fermenting in the basement, and store most of my brewing gear down there too, it's even easier. No more lugging 6.5-7 gallons of finished beer, in fermenter, up stairs, then onto a table in order to transfer to a bottling bucket (hope you got the seal tight on the spigot) and such.
BTW, with using 3 gallon corny kegs, transporting is really easy. I'm also working on making a portable kegorator to use later. That is, if I go someplace where there's enough people that will drink, and enjoy, my homebrew to have it make sense. Otherwise, I can simply fill a few bottles to bring for me, and a few others, to enjoy. :rockin: