Why can parties require a minimum item level that's impossible to reach?

With regards to Square Enix trying to crack down on advertisement slots in the Duty Roulette tab of the Party Finder, wouldn't a design decision that would help and should be pretty easy to implement be to simply prevent the minimum item level from being set to higher than what's maximally possible at the moment? I can't think of any good reason why a party should have say a minimum item level requirement of 999 in order to join; it makes it impossible for the party to be joined and thus makes advertisements more likely as a result.

Limits I think would be reasonable to impose on a PF listing's minimum IL:

• PF required IL cannot be higher than party leader's IL
• PF required IL cannot be higher than the maximum currently attainable IL

Requiring a minimum IL higher than you yourself have is probably rude.
Requiring a minimum IL higher than anyone can attain means you obviously don't want the party to fill and drop from the listings, so it is some sort of advertisement. There are legitimate uses for this, e.g., inviting the whole DC to your FC's holiday party or a tasteful memorial; however, it seems like these are far rarer than people advertising for illegitimate things.