> That is, why is the user forced to update in order to use the application, even if no critical security issues arose?

Because they’re adding new features, both security improvements and user‐facing sugar.

Moxie’s thoughts on this are well‐known: he believes he can build a better and more secure messenger by keeping deployed clients as closely aligned as possible. Even if you disagree (and plenty of people disagree, as we see in almost every Signal comment thread), it’s at least a valid opinion to hold. https://signal.org/blog/the-ecosystem-is-moving/