do computer experts know not everyone has a mobile phone?

There are all these sites on the net that ask for your mobile phone number.

A mobile phone is expensive compared to a regular telephone. There are plenty of guys who bought a computer so they can watch pornography, and are now porn addicts. These guys have nobody they want to talk to, so a mobile phone is a waste of money.

The guys who write a program that asks for a mobile number that does not exist are stupid. Is there some kind of number that can be used as a prank, so like if anybody calls that number they will be talking to someone who is trying to sell them an erection pump?

i would imagine they do. But we live in a society where people used their mobile phones ore than a computer nowadays

Software is written for the majority of users, not the minority.

The majority of users have mobile phones.

no they do not