Depends on the age of the child.
Depends on the venue/place of the party.
Depends on IF there are in fact, adequate amount of adults/Hosts at the party to supervise ALL the kids that are invited per the venue. ie: if a parent has a party for her kids and there are over 10 kids, and only SHE is the only adult "supervising" all the kids and doing the party too, then no, I would not leave my kid there and drop off. There are not enough "eyes" to watch all those kids. BUT the Host would have to say.... that the parents of the invited kids, can stay, or not. If it is a drop off party, or not. AND it depends on the age of the kids.
Most parties my kids gets invited to, there are the Hosts there, PLUS, an Aunty or grandparents etc., so that there are other "adults" there HELPING with the party and the supervision of the kids. So to me, that is enough. I do not have to stay. And I don't.
And these are drop-off parties.
I never, stay at a party, UNLESS the Host has made it clear, that the parents can, stay. And even at that, per the ages of my children, I do not stay. I drop off.
My kids are 7 and 10. So at those ages, parents do not stay at a party. They drop off.
Even when my son or daughter was in Kindergarten, I dropped off.