if you listen to ATC here https://www.liveatc.net/search/?icao=UUEE you can hear that sometimes it is done in order to get around sanctions since an emergency aircraft will get assistance and be allowed into prohibited airspace no matter what. Sometimes the pilot declares a general emergency and ATC just gives them landing priority, the instances when they don’t say a reason are likely in protest as many pilots are flying on non-airworthy jets which are not able to be serviced since no country is willing to sell them any parts. Squawking shows up everywhere and many people get special alerts when there is a squawk.