What does a scammer do if he/she gains access to your computer?
They can do a number of things to your computer. If they are smart enough, older versions of certain remote-access programs can create backdoors that could potentially let viruses, and all sorts of malware and trojans on your computer.
They could potentially delete all your stuff, gain access to passwords and online bank accounts if you use online banking. So on and so forth.
Basically a lot of bad, and intrusive things could happen so it’s safer to just call and mess with them if you do not have a secured virtual machine and do not know what you are doing.
Stay safe out there!