FWIW, this was my biggest gripe with it too. I did not start using WhatsApp till 2014 while all of my friends had already switched a couple of years back. I was happy with Facebook messenger, but i was forced to switch to be in the loop. Although since Facebook messenger also needs your number to verify the phone, if I remember correctly, it hardly matters.

I have recently made the switch to Signal[1], and made my partner switch too. It's been a blessing.

[1] https://whispersystems.org/

Same here.

I have two phone numbers (one in the US and one in Austria) and also spend a considerable amount of time in both countries each year. I'm usually reachable on both numbers (and usually only give the local number to people in each country), with one number forwarding to the other number.

With WhatsApp I can't link both numbers at the same time. Even worse, according to the FAQ there's a limit on how often you can change the phone number linked to the account, so it's not even an option to just always change it to the "local" number.

I like that WhatsApp is tied to my phone number. It just works. That's the one of the biggest reasons of its success.