Let's take Call of Duty as an example, it's is the biggest after all.
Download only there are episodic releases, $10 for each campaign part split into 3 or 4? $30 for just multiplayer and maybe $30 for only Zombies.
If you want all 3, then $90 is well out of order. Many people only play multiplayer, in the case of CoD most people might just download mulitplayer only and save $30 from retail, which means developer makes less money.
If they were going to do it, they'd have to do a $60 retail version as well but because most people only play multiplayer, they'd still make less.
And it has to be a bloody good main story games for me to buy anything digitally in parts which cost more than a retail game. I ain't a fool and neither are most other gamers.
In theory it's good but customers are a fickle bunch...
Hmm, pie.
