There is a reason to don't use 3D API.
Only computers in NA, North-west EU and Japan support them...
I live in Brazil for example, my sister computer is new, has a multi-core processor, several GB ram, and yet it does not run OpenGL games.
I for example can only play Dwarf Fortress (use OpenGL to render ASCII graphics) on my own computer, on any other computer I find it runs crawling slow.
And this is not a issue only with Brazil, I asked people around, and it is common in several places of the world... The population that actually own OpenGL or Direct3D compatible cards is a minority...
Only that this minority get more attention from companies...
But if you are targeting only these "traditional" markets (NA, Northwest EU, JP), then go for it!
EDIT for those downvoting:
Obviously you disagree, so, do you have PROOF that NOONE ships anymore computers with crappy VIA or SIS chips (or even other unknown or worse manufacturers) with none or only OpenGL 1.0 support?
I have TWO machines like that in my house, and they are new (both have more than one core, both have 2GB ram, both have clock frequency above 2GHz...)
My university have 200 machines like that, even some Dell-built ones.
It is plainly simple, GPUs are expensive (even crappy Intel ones), and in poor markets, it is a luxury, people buying machines to run MS Word and read e-mails are not going to buy a machine with a decent graphic chip when they can buy one that is 50 USD cheaper, specially when 50 USD is what most people have to buy food for a entire month.
PLEASE, don't come here saying that I am saying BS, if you never visited a third-world country, and also, don't say that third-world country people don't play games, they do, a lot, Osmos developer post about the Linux version launch of their, pointed that lots of incoming traffic (actually, most of it) was from Russia, plainly because those people are usually ignored.
Here in Brazil, the most popular game is Counter-Strike, running in Software mode... Some Lan-Houses have only 10% of the machines with GPU, even big-ass ones with 200 or even 300 stations...
I should not have posted on this, I knew that it would attract down-votes, I got free loss of points for posting this, every time I explain why my other game uses Allegro 4.4 instead of 5.0 because 5.0 does not support Direct Draw or software mode I get lots of flak from lots of people saying that I am a sort of liar or that I am stupid for saying this truth about the actual availability of OpenGL acceleration.
EDIT 2: To be able to play and develop games that have OpenGL, I had to beg for my parents and other people to buy me a GeForce 8600 (that was the cheapest card that I found that still could ran Mass Effect 1 and other UT3-engine games), they bought me one, but now I am several years without ever getting other gifts again, not even birthday presents, because of how expensive it was, and I hope this card work for more 3 or 4 years...
A pratical example: Eletronic Arts made a new client for Ultima Online that uses 3D acceleration for its 2D graphics... Result: Lots of players complaining of ridicously low framerates, and EA backing down in their decision to enforce the use of the new client (now it is allowed to remain using the old one)
EDIT 4 in 2015:
This reply will be left here mostly as historical artifact, currently the amount of computers with extremely crappy chips is low even in third world countries, they still do exist, specially in office-aimed computers, but they are not that common anymore, I don't think it is worth working with Software-mode APIs anymore, OpenGL-based APIs are the way to go now.