Well it should be clear but let me explain then.
He who has the money makes the rules.
If i as a company want my product to make money, i have to figure out the audience.
Once i figured that out, i start making it fit their workflow. If it slots in easy, they switch, if they switch i get paid, if i get paid im happy.
Now, the indie creator market has free tools like capcut and other small scale editing softwares. A good majority, as the barrier to entry is so low, have no money for professional editing software.
Because of low funds, hobbyists stick with free tools. The pro/broadcast market is smaller in raw numbers but massively higher in value they need 29.97. If Adobe defaults to 30 just to satisfy casuals, they risk alienating the paying base that actually drives revenue.
There are 0 numbers saying what % of premiere pro users are hobby/professional. You will see based on what circle you’re in. I know a ton that use it professionally.
You, making a capcut style product, are geared towards hobby creators and should default to 30fps. Your main target audience is not industry professionals.