Regionals is a family reunion of skiers. You get to see those crazy cousins that live in the other state. Families always consider activities for all kids, teens, and adults. That's why it is fun. Sure, there is competition during the day, but there is social time in between and afterward.
Nationals has typically been attended by these types of skiers:
1) First-time qualifiers who can afford to travel
2) Podium Potentials - majority of the Top 10% of the division by ranking (who can afford to travel)
3) Other qualified skiers who live within a reasonable distance (and thus can afford to travel)
4) Other qualified skiers who can afford/justify travel
5) People who plan their family trip in conjunction with nationals
I don't see much deviation from the above. The members of each of those groups will change each year, but those groups seem to be well represented.
So, if the Regionals participation requirement was dropped, who else would go? Would the number of members in the above groups change that much? Did I miss a group?
Possibly fewer ranking-list-qualified skiers would attend regionals, creating room for lower ranked skiers to podium at regionals creating more first-time qualifiers, assuming they also meet #3, #4, or #5.
Possibly a few more Top 10% skiers might go assuming they also meet #3, #4, or #5.