I Thought it was because of Steven Hillenburg's 3 Requirements for his show:
1. We must NEVER find out the identity of Pearl's Mother
2. Spongebob must NEVER be allowed to get his boating License
3. the series is NOT allowed to have any Crossovers or Spin-offs(*cough* Kamp Koral *cough*)
I'm Going off on a tangent here; but Seriously; out of Steven Hillenburg's 3 Mandatory rules for his Cartoon; The Only 2 Rules that Nickelodeon is STILL continuing to follow to this day(as of 9/23/2019) are the first 2; They Still haven't revealed the Identity of Pearl's Mother; and whenever Spongebob DOES get his Boating license, it's always taken away from him by the end of the episode as the status quo is still upheld to this day, for better or for worse