You are right that they could change jobs, but since Google and Youtube are prestigious global brands, future employers are likely to assume those jobs are well

You are right that they could change jobs, but since Google and Youtube are prestigious global brands, future employers are likely to assume those jobs are well-compensated and that if the person left, the fault lies with them for some reason. This too is common sense. Anyway, I see no reason why people shouldn't consolidate their labor power in negotiation just as corporate shareholders consolidate their capital power.