Because we all saw where it leads with Google/FB. They might start by just doing the simple things you proposed. But once a government or bank is a customer, they would be the largest/most powerful customers by far. Meaning Signal would begin to bend to doing what those customers want, maybe collecting analytics or personal information, or selling your contact data to advertisers. Maybe one of those banks donates money to Signal and wants favors in return.
The biggest customers of a company inevitably shape the incentives and behavior's within that company. easy to dismiss as a "slippery slope fallacy" but it's historically true. No one who's using Signal to get away from the shitty enterprises that built/own FB Messenger wants a repeat of the same thing. Even if you don't agree, many Signal users probably do, and it would be silly for Signal to piss off their customers.
The biggest customers of a company inevitably shape the incentives and behavior's within that company. easy to dismiss as a "slippery slope fallacy" but it's historically true. No one who's using Signal to get away from the shitty enterprises that built/own FB Messenger wants a repeat of the same thing. Even if you don't agree, many Signal users probably do, and it would be silly for Signal to piss off their customers.