Philosophy
I've recorded in studios, and I've engineered projects for
other bands. One thing that always struck me was how much
most "professional" recording studios resembled dentist's
offices. They often had a receptionist, and bad art on the
walls. Carpet and lighting seemingly designed to intimidate,
rather than inspire. If you got hungry, the only option was
to order out. If you got tired, you could try to find a
quiet spot to lie on the floor, or you could leave and go
home.
Which brings me to my point: Most bands practice at home, or in a practice space. They are comfortable there, familiar with it. And if there's one place a band will perform well, that's it. So why not record there?
Traditionally, recording at home has been rather expensive, and the results have been less than stellar. Nowadays, though, with digital technology and portable rack gear, it's possible to have the exact same recording quality as any studio, at home.
So why not just buy ProTools and record yourself? First, let me say that if you are interested in recording, you should absolutely invest in learning about it, and doing it yourself. It's very enjoyable, and satisfying! On the other hand, engineering is just like playing the drums or any other instrument. The ability to go buy a drumkit doesn't make you a drummer, and buying a bunch of recording gear won't make you a recording engineer.
Also, there is an advantage to having another set of ears to hear you. One of an engineer's main responsibilities is being objective, hearing your music the way a listener would. Of course, who that engineer is makes a difference as well. Do they like your music? Are they familiar with the genre? (personally, my tastes range between punk/indie/alternative and garage/surf. I'm a big Shellac fan, and currently, I've been listening to the Pixies (Surferosa is probably one of the best-recorded albums ever, in my opinion), Blonde Redhead, some Unwound, and whatever comes across my speakers on the internet radio stations I listen to.)
So having said all that, my philosophy of recording is simple. Get the best recording of the best performance, and do it the most efficient, enjoyable way possible.