While there are lots of reasons to not want to use Facebook, it's also pretty reasonable that refusing to use a potential employer's product would be pretty much a non-starter when it comes to employment.
How would that work being a new hire at Tesla considering that they probably pay a lot of folks less than is required to own one?
Cars, appliances, housing, fuel & energy, food, etc. Huge, huge swaths of the economy don't require brand loyalty because it's not reasonable to expect.
But in more modern times, there's certainly a general expectation to use your employer's products when it's reasonable to do so even if they're not your preferred options. There are exceptions of course and tech companies are usually more flexible these days.