'There are very few films you will do with so why pay all that money just for them to sit on the shelf'
That's your view. I'd guess that those of us that do
'collect' (select) DVDs would select those that, yes, we would want to watch again and again.
There are people who can only read a book once, and there are those who can read a book time & again; you get different angles, develop different interpretations and understandings, and notice subtleties you hadn't noticed before.
Same with movies.
I've got a mix of Indie and 'mainstream' stuff:
Natural Born Killers
Proof of Life
The Man who wasn't there (Coen Bros.)
The Shining (Kubrick)
Eyes Wide shut (Kubrick)
The others (Amenabar)
Carry on Abroad (had to have at least one Carry On
Big Lebowski (Coen Bros. my favourite)
Monty Python - Holy Grail (wickedly funny)
Passenger 57 (terrible, terrible, terrible, but thus comical)
Rabbit Proof Fence
Bunch of 5 (Norwegian "Schpaa")
Shipping News (no one likes it except me)
Amores Perros (Mexico)
Out of Africa (a big mistake, you can have it if you like)
Jurassic Park (ok, it's very Hollywoody, but a classic)
Happiness (cruell, disturbed film, but funny)
Full Metal Jacket (another great Kubrick)
Dr. Strangelove (spooky/made me uncomfortable)
The Eye (great horror)
The Human Body (BBC Docum.)
Bugsy Malone (for old times' sake..)