You're confusing telemarketers with phone scammers. Phone scammers try to call you to install malware or steal you CC info, etc. Telemarketers call you to try and sell you something or get you to donate to the police union.
Telemarketers are poor schmucks trying to work a job. Their companies generally will abide if you request the do not call list. Scammers probably will not.
Any call I get that starts with a robocall from "Ann" or "Rachel" or "Barbara" from Cardholder Services, or Account Services, or Microsoft Tech Support is basically fraudulent from the start . Robocalling is stricly controlled, and I use Linux. Next, we have Caller ID spoofing, some of the area codes are non-existent, and maybe the number is of the wrong format. After that, the failure to identify who they work for clearly is a big red flag, as is the use of names like "Edward" or "Candy" for people with South Asian accents.
Even before the no-call list became effective, there wasn't a lot of difference between a telemarketer and a scammer. For several years, I politely asked for a written copy of their no-call policy, every single telemarketing call. I got one. Telemarketing was a very shady grey area business long before the fraudsters made it legendary.
Telemarketers are poor schmucks trying to work a job. Their companies generally will abide if you request the do not call list. Scammers probably will not.