The original reason for both plug type and PAL was simply different electrical systems.

Plug type ensure you didn’t plug a 110v appliance into a 220 system, which could be gangerous to the person.

PAL vs NTSC was really just because PAL came after NTSC and attempted to fix some of the color issues in NTSC, but also had to work on a completely different electrical system - and both relied on timing elements within that electrical system.

It wasn’t “lock in”, it started because the two electrical systems were very different (even the prior black-and-white systems were very different for the same reason, 220v at 50hz vs 120v at 60hz). This frequency difference means different timing mechanisms and even alters the number of scan lines.