Vesuvia, you can google the history of cheerleading, but anyway...
Cheerleading started out as a varsity amateur activity. It spread into high schools. As universities became co-educational, cheerleading stopped being a male activity and became a co-ed activity. Amateur cheerleading also happened at professional football matches. Then in the 1970s a football team owner of the Dallas Cowboys decided to make cheerleading professional. He auditioned only female dancers rather than cheerleaders and dressed them in skimpy, sexualised outfits. Other NFL owners did the same later on.
University cheerleading squads remained co-ed and became more and more focused on the gymnastic stunts - so there became a division between cheerleading as a sport which students can get scholarships to the best cheerleading universities to join their squads, and pom dancing done by commercial groups like the Dallas Cowboy cheerleaders.
I very much doubt that the average UK school pupil has ever heard of the Dallas Cowboys. Cheerleading as a sport appears in many tween films such as Bring it On. Sexualised pom dancing isn't taught in US schools and so has no reason to be in tween films. Films like Bring it On are among the few tween films that pass the Bechdel test.
Lots of primary schools and secondary schools in the UK now teach cheerleading. Both my DS and DD did it at Primary school where they were taught by both male and female cheerleaders. Just like ballet and other dance disciplines, in the younger years there are lots of girls, but in the older years in competitions and performances, there are more boys/men as they are integral to the team for lifts and partnered work.
It would be pointless to call it another name because it is not just dance and gymnastics - it is a specific style of dance and gymnastics that has been created and developed by cheerleading squads over many years. In much the same way, Jazz has developed from a fusion of North American and Caribbean dance styles and has become a specific style that we continue to call Jazz.
It is generally an advantage to be small and thin if you want to be a competitive dancer, cheerleader or gymnast, but for obvious reasons to do with the physical demands of the activities. In much the same way it is useful to have long limbs for rowing and climbing, and to be tall for Basketball.