You can buy "anonymous number" on fragment without using any client and without providing any personal information and use it as much as you can

When signal becomes at least remotely as popular as telegram it will implement same protection to fight against spammers because you can't have free unrestricted registrations and don't drown in spam

Telegram currently makes it as accessible as possible: either use it freely but register using phone number and official app or pay and use anonymously as you want