I also wondered if it had something to do with 60Hz electricity in North America vs. 50Hz elsewhere, and how this would relate to 25fps vs. 30 fps and NTSC vs. PAL.
In the days before silicon transistors and quartz clocks, the most accurate clock available was the mains frequency, so to make it easy to decode the frames without the TVs going out of sync whenever the weather changed, places that used 50Hz mains used 50fps and places that used 60Hz mains used 60fps. The choice of NTSC or PAL protocol was a separate choice which depended on where the equipment was bought from, Europe and everywhere that bought European equipment used PAL and most of America used the USA's NTSC, except for some south American countries which decided to use PAL at 60fps either because it gave better image quality than NTSC or because the people that decided wanted to make the equipment incompatible with any that could be imported - lots of money to be made selling TVs when there is little competition.
If you still use an old vacuum tube TV then there will still be a problem if you want to play 50fps PAL using 60Hz mains, but any modern TV using silicon chips will have no problem.
The only real problem these days is that some of the big companies like Sony sell video cameras that use only 30/60fps in NTSC countries and only 25/50fps in PAL countries so depending on which country you bought the camera in, the fps may or may not be compatible with video from a 60fps action camera. If you want to be able to create a video containing footage from both cameras then it is necessary to set the action camera to 50 or 60fps to match the Sony since the Sony doesn't provide the option. This issue has nothing to do with the analogue PAL/NTSC standards, it is just a frame rate issue with the digital video files, however the option to change the fame rates may be called PAL/NTSC.
