Cover Albums – what are they good for?

The last few days I have been playing the “Through The Looking Glass” album by Toto a lot. And despite being a huge Toto fan (seeing them live on numerous occasions and owning all their releases), I kept thinking I was not sure I actually like this release. Which again led to the question why known artists record and release an album with covers anyway.

I mean, the last couple of years has seen several of those coming to surface (besides Toto, Rush and Queensryche come to mind, but there are more) and I really don´t see the point. Sometimes it is said to pay homage to the songs they grew up on. Nice, but why not encourage people to buy the originals? Post a message on your website!
Sometimes it is to have something on the market while on tour. I am thinking with better planning this could be avoided. Or release an EP. Value your fans!
Sometimes it is just because they want to. Come on, I prefer original material, sit down and write some!
Sometimes it is just because an artist made a not so nice comment… Yeah, that´ll show them!

For instance in the case of Toto they cover Watching The Detectives by Elvis Costello. And Costello publicly admitted to hate Toto! And to be honest, their version adds nothing to the original, which isn´t the best Costello song anyway, but that is just my opinion. So why bother?
And something else, if one decides to put out a cover album, why not put in some conscious effort to make the chosen songs your own? Is anybody waiting for a note to note perfect rendition? Why not recreate it so the song sounds home made? There are a lot of examples that show that can be done. And make it a much more pleasant listening experience. Like Toto´s beautiful version of While My Guitar Gently Weeps (George Harrison).

Is it just me, or what do you think?