I don't see why not many people see the appeal of prepaid SIM cards. Just buy an unlocked phone, and pop in a prepaid SIM card or install an eSIM profile. That's all it takes.
I rarely make phone calls, and haven't send an SMS in years. WiFi is everywhere, so all what I use the SIM card is to register with shitty 2FA providers that dont support TOTP/WebAuthn. The catch with prepaid SIM cards is that phone calls, SMSs, and mobile data are quite expensive. My carrier charges 9,95 euros for a 1GB bundle. I only use mobile data when I need to look up directions or something small that even a small package with a small data cap, or a package with unlimited data at slow rate does the job.
Context: Netherlands, using KPN prepaid. I understand postpaid packages are more common in the US and prepaid cost a lot more too.