Lite Versions

How come most devs don't release lite versions when there games come out

some do some don't...many focus on their full game before putting effort on a lite and they prefer to get their game out as soon as possible

Some lites do not help sales of the paid game. A few have been pulled from the store. Gameloft usually waits awhile before releasing a lite.

Probably because the nature of the app store works against you.
You can't be sure when Apple is going to approve an app. And setting a release date far in advance does you no good because of the way the listing system works.

So you worry about getting the main version out first, and the lite second.
If the Lite gets out first, by the time the main gets out people have moved on.

If the approval/listing service was better designed you could just submit with a fixed date for both and not have to worry about being approved a week before and having that bury you in the what's new list.