It might be so...and in your case here it might seem dumb.
But in other cases it might also just lock some Ink around with a lot of dead profiles.
If a new creator just came in and leave again quickly because the person isn't serious, and got some ink, but not enough to cash out with the 25$ minimum, the Ink will just be stuck on the dead account and you have just wasted you support.
With the commitment of having a minimum subscriber or the commitment of active e-mailing the boss. You know this creator is for real and your support Ink isn't waisted.
But getting Ad Ink with 100 subs and Support Ink at 250 subs might be a little out of balance.