The thing about streaming is that you generally can't take it with you. When I'm reviewing albums I often want to hear them more than once, because I may not form the correct opinion on first listen: I might hate the album but then grow to like/love it, or even sometimes vice versa. If I have to be at my computer all the time to do this then it's a little restrictive. Also if I'm at my PC I'm probably doing other stuff too so not giving the music my undivided attention.
I come from the age in which you had no choice: you listened to music you liked on the radio and then if you wanted it you bought it, or if you were very lucky a friend had a copy and you could tape it. But I must have spent thousands on albums, tapes, CDs over the years. That was when I was working. Now I'm not, as such, so I can't afford to just buy what I want, so I download what I can, and steam what I can't. Does that make me less a fan? Let's see.
I just last night experienced Slowdive for the first time, on Spotify. Now I liked them so much I'll buy their albums or download them, because when I stream something and like it I want to have a copy I can play whenever and wherever I like. Does that make me more, or less, a fan than someone who's been into them since the beginning and has all their albums? I don't know, but even if I didn't buy their material I would still at this point consider myself a fan, because I like their music.
Sometimes there are albums we would like to buy but the financial realities intrude: I'd rather have a roof over my head thanks...