Well many of them are judges.
Out of curiosity, just to nitpick, where are you/what level of coaches and judges are you talking about that many of the coaches are judges?
ISU judges need to be "eligible persons" just like skaters. Until fairly recently, that meant amateurs -- no income from skating-related activities.
More recently skaters are allowed to coach and still maintain eligibility.
However, according to current ISU rule 102.4.b, "Paid employees of ISU Members and their affiliated clubs,
and remunerated Coaches, may not be a Referee, Assistant Referee, Technical Controller, Judge..."
Within US Figure Skating, judges are not allowed to coach except 1) in learn-to-skate programs, skaters who have not passed pre-preliminary or higher USFS tests, or 2) if they're full-time college students.
I don't know other countries' rules, but there are no international judges who are also full-time coaches.
Coaches are allowed to become technical specialists (or technical specialists are allowed to coach, whichever way you want to look at it).
ISI competitions use coaches as judges. This is a recreational program completely separate from the ISU and its member federations that uses their own set of rules.
Are you referring to coaches who are tech specialists not judges, or coaches who judge ISI competitions?
My point is many people who work or involve in professional judging or coaching actually don't watch all programs they could.
Now this is very true.