Unions are a modernization of guilds, and guilds arose to protect skilled and semi-skilled professions back to the Sumerians. "Tech" has become anything involving software in any way, shape or form and my washing machine has software. The reasons tech workers have largely been immune to organization up to now is it's a young industry historically fueled by passionate nerds who can be tricked into working too hard for someone else's "vision." Your every argument is a canard for "Tech Is Different™" which is the same oligarchic argument that turned "Luddite" into a pejorative in Elizabethan England. If I can't order a burger without a QR code? Tech is no longer different.
1. What does your Apple Retail Store Union membership get you?
I haven't seen the contract but I'll bet wage floors, benefit vesting, retirement and those things that salaried Tech™ workers view as their just due and feel totally okay denying freelancers because they haven't "paid their dues" (lol). Right now, the Tech™ industry is busily defending Amazon drivers pissing in bottles.
2. Why would they even allow you to stay in the union if you weren't working at an Apple Store?
You work in a union when you need or want union benefits, depending on the labor laws of the state you're working in. You pay your dues, which the union uses to distribute benefits. When you no longer need union protection because you are not doing that labor, you take honorary withdrawal and your benefits are managed in perpetuity (IATSE locals in LA) or dissipated into corruption (IATSE national in New York, I ended up in both).
3. What benefits did you accrue in your 2 years as an Apple Store Genius that is going to help you when you retire?
Fuck, dude, time off, wage protections and a retirement plan. What's so alien about this? You buy groceries from union members and you don't even know it, why are you scratching your chin about the same protections being offered to people selling iPhones?
I'm optimistic that young tech people are unionizing.
Your mind has been SO POISONED that you think schlubs at the mall hawking iPads are "Tech™. The fact that the Apple Store workers in Towson are technically machinists matters not a whit - GEICO is the Government Employees Insurance Company and errbody can buy in.
This is literally a bunch of people whose lives are being squeezed by Tech™ insisting that they deserve as much protection as grocery baggers and you're looking at a Brave New World.