Some girls do great without them. Most don't, once they hit a certain size and level. You're just not going to see average sized high school aged gymnasts doing the level 10 skills without dowels for the most part. They're generating more force and the dowels help with that. But smaller level 7s, most of them should be able to do it. The main advantage is getting used to dowels sooner. And I find this to be somewhat of a significant advantage, honestly, but when the gymnast and coach intend to make that conversion could be planned any time or if well planned take place over a longer time span and result in very little lost training. My personal preference would be to take some of that effort out of it and have the kids transition earlier.
There have been international gymnasts not using grips. My observation over the last quad is that these are becoming fewer and fewer. Looks to me like most of the Chinese team is in grips now, from what I remember (I don't watch gymnastics all that much, but I seem to recall noticing that). My own take on that would be now that the age limit has been 16 for a full cycle, we are seeing more and more training practices adapted for gymnastics to be able to peak later. If sr int'l competition will be at 16, 17, 18, it makes sense to get you grips at 14 or sooner now. At 16, 17, 18 even if you're pretty small you won't be 13 or 14. Look at Nastia, Chellsie, Beth etc. These are very fit gymnasts (and good at bars), but there's virtually no way you're going to be an 80 lb 19 or 20 year old, especially carrying all that muscle.
Also, as far as the rip thing, grips can help that but some people are prone to ripping and some people aren't. I got some rips in L7 when I started swinging, and after that I didn't rip once. It's been years since I've had a rip. I get up and play around swinging on men's high bar without grips and I don't get close to ripping. I don't do anything to take care of my hands, and I do a lot of the "nos" I've seen like putting lotion on (I hate the feeling of chalk soooo much). Some people wear grips from L5 on and continued to rip all through high school weekly, wrist rip problems, etc. I think a lot of times that variable can be pretty related to skin type. I have pretty dry skin on my palms. Grips don't really make a difference for me when it comes to ripping or any other hand problems.