The corp gives you the "purpose" in some instances. Joining an ambitious corp can be your own storyline.
Early on in my career, I joined a pirate corp that hung around low sec and PVP'd other corps (piracy!). Eventually, they decided it would be fun to move into null sec, and from there we got caught up in alliance politics and joined a war for the region. It was a blast. I logged in nearly every day to see what fleet ops were going on or to enjoy the rich bounties null sec provided.
There was no specific goal for me or the corp other than to PVP and have fun. Find something you want to do in EVE, (make money, produce things, explore wormhole space, blow stuff up) and a corp that supports that goal, and you will have loads of fun...typically.
I say that because EVE is not for everyone. Some people just refuse to have fun with the game. But there is a lot to offer, YOU have to find it though. YOU (and others around you) make the experience.