Why wouldn't the same mechanism apply for banks? There are also a big variety of banks to chose from and people tend to pick one and stick with if for a while.
But you don't see BofA/Chase/YouNameIt fanboys.
2. What companies you choose can be seen as a single pieve of what some perceive as an ideological struggle. Google the defender of openness, and Apple the harsh dictator, managing user experience with an iron fist.
3. People have their phones nearby nearly 24/7. It's possible a subconscious attachment to it develops in people, though I don't know the psychology of it.