Some steam games are always online?

Most Steam games require Steam to run at the same time as the game, although it's usually sufficient with Offline Mode for those.

You need to have your steam client open and logged into the account that owns the game and THEN switch to offline mode. That works for most games, but some you really do need to play online. It's a third party thing I'm sure. It pretty much is like the Xbox One bullshit but Steam is a free optional service with dirt cheap games so people care about it a lot less than they did for the console doing it.

Steam games have cloud sync for save data and stuff like that. Games like Super Meat Boy or Cave Story+ do not have it at all.
You can always get some Humble Indie Bundle games and download the free-DRM versions of those games, but remember, you aren't going to get Steam achievements or cloud sync at all.

You can sync the data later if you connect, only if you play on Steam offline.

since i use steam on two computers i get the trouble of not being able to be online on both my desktop and laptop (which is significantly more powerful) at the same time even though i play games on both...

the way you get around it is log into steam once with your account so it syncs the computer to your account (you can sync multiple computers to an account but it isn't necessary to do it with all computers you use steam on). then, next time when you want to play the game but don't have an internet connection, you will be given the option to "sign in in offline mode" which allows you to still play all your games downloaded to your computer, except without achievements and storepage, etc. (since they aren't stored locally)

if it really bothers you though, buy the game, then download a cracked version (since you own the game you are allowed to do so legally but it is frowned upon severely)

a little annoying to do, yes, but i hope it helps your predicament.

Some work with offline mode but indeed some games do require you to be online.

The first time you run a game you need to be connected online. If offline still doesn't work then either you haven't configured it properly or steam is being buggy again.

WAT WAT WAT ?

(I'm pretty sure, 99% of the single player games/modes on steam can be played offline.)

-_- Oh my god.