For me, part of the fun of a TCG is physically having/looking at the cards. I couldn't see myself blowing that much money on digital pictures.
That used to be me. I cane back to MTG briefly a few years ago after having not played since I was in school 15 years ago. At first I was all about collecting physical cards- I bought booster boxes, openned, sorted, sleeved cards, etc. Bough some singles on ebay. It was fun.
Then I decided to try MTGO, because I like playing draft but local stores only run drafts once a week. Didn't notice a huge difference drafting, felt like much the same game, similar costs, etc.
After being back into the Magic scene for a few months, I had enough drafted cards that I was interested in building constructed decks on MTGO, I realized just how convenient digital cards are. Using the same cards in multiple decks, no added expense of card protector sleeves, no worry of cards losing value due to wear & tear over time. Vastly superior trading marketplace. It was better in almost every way.
Admittedly, I still like the feel of shuffling real cards, and it's more fun to play in person. So I decided on a compromise. I'd primarily play and collect online, and if I ever developed a highly successful deck I'd simply purchase the physical cards to recreate that deck for physical card games. Since then I came to my senses and realized playing Magic at all was a huge extra expense I really didn't need to deal with, so I haven't played the game in the last year, but if I did come into a situation where I had an extra $300+ to blow on a hobby like that I'd be playing online.
Oh, and re: Hearthstone, why no Android version? I'm starting to wonder if Blizzard has a lot of Apple fans in charge of making those sorts of decisions.