Should I include the names of my Master's and PhD supervisors in my CV?

Additionally, your supervisors might have written you letters of recommendation for grad school (or could in the future for other grant applications). Thus, mentioning your former supervisors is a form of acknowledgement and transparency for other researchers or research institutions.
I totally agree with the former comments that in 90 %, it won't harm you.
In case you are completely unsure, you could ask your former supervisors whether they are okay with it (but I would be surprised if there is an academic scholar who says no)

Unless your Supervisor(s) are well known in the field, it would not help much to add them. Since every PhD has supervisors, it won't add any more value to the CV.

Also, if your Supervisor(s) enjoy any degree of clout, authority, cult status, following, awards & recognition like Fields/Nobel/etc, it would add a lot of value to your CV.

It would, however, be a good practice to add their names to a separate 'References' list at the end of your CV with contact information. Supervisors are great go-to sources for information on a scholar's work ethic, performance record, 360-degree assessment, etc and providing transparent references instead of 'references will be provided on request' can send a signal that you have nothing to hide.

All the above are very subjective, however.