TOTP is both more secure and cheaper to implement since you don't have to pay for text messages or directly communicate with the 2FA device in general. Honestly whenever some obsecure app or website demands my phone number as the only 2FA option I immediately assume it's a front to get my phone number for data brokerage. Like no way does a random online game or something care so much about security to demand 2FA but then proceed to choose the least secure and hardest to implement option. There's another reason.