Many have issues with stability. Especially with firefox which comes installed via snap on ubuntu. Similarly compared to deb snaps versions occasionally have weird bugs. I personaaly had an issue with opening files properly using snap but worked fine on deb.

Also its unnecessarily forced. Deb works great and apt is widely used as primary package manager. No need to maintain the system with another one in the mix.

Its also repoted not to work well on otknr platforms like fedora or arch. Other package formats like AppImage, flatpak might be better in that regard though I havent used them.