Just because virtually every team does it doesn't mean it's a good idea. It ties up too much money into a volatile position that rarely pays off. Has Howard 'earned' his contract? Has Rinne? Rask? Lundqvist? I don't think any of the 7m+ goalies have done anything close to earning it. I think a lot of skaters who make that much have earned it though.
Yes, yes, yes, and yes.
All of the above have earned their contracts. Howard is the closest to have not, but even he has. I don't think you need to have won a Cup to justify the type of contracts that these guys have gotten. Rinne has been a big part of what Nashville's doing and any success they've had. Rask has put Boston in position when they've got their other positions sorted out to make a run at the Cup. Hank Lundqvist has routinely had the Rangers in the latter rounds of the playoffs. Just because they haven't gotten over the hump shouldn't be a "this guy isn't worth his deal" type of thing.
Playoffs are best on best and weird things happen. The best you can hope for is that your guy gives you a chance against the very best that are out there. Each of the goalies you have mentioned here did that.
Goalies are a weird position. It's volatile and having the best one does little more for you than having an okay to good one... however, if you have a crap goalie, you're not winning a damn thing. If you try to make it through the season with Chris Osgood + Ty Conklin like the Wings did in 2009... you better have a team that is loaded for bear literally everywhere else. Goalie is certainly the position that you could spin the wheel at going with a cheaper guy to get the same production, but it's also a position that could tank an otherwise promising run if you're wrong.
