They play the regular season because it generates a lot of money. If the owners thought they could play nothing but playoffs every year and still make as much money, they would. They want to maximize profits, even if it doesn't improve (or may actually hurt) the quality of the game. Just look at the talks of the NFL increasing the length of their season.
It's much more difficult to make the Playoffs in the West than it is in the East. The East has more "top quality" teams while the West really has only 1. But in the West, you have heavy depth in the 2nd tier teams. 2nd tier teams from the East would be 3rd tier teams in the West. West has more 2nd tier talent, East has more 1st tier talent
I agree, sans Kobe, they're just another Playoff team...it all depends on Kobe. I just don't think Kobe's ready to go quietly into the night at age 31. I hate to say it, but I see at least 2-3 more years of the Lakers sitting on top of the West. There may be challengers but I don't see any West team that has it together enough to take them out. And really, what's to stop them from winning 3 championships? After this year, the Heat will most likely be the only team that can challenge the Lakers as the Celtics core hits 35. The NBA truly is a mess right now, and we can thank the Grizzlies for screwing it up for everybody.