I'm not sure if you mean why I haven't switched or why switching is good.
On the first, laziness, and covid have impacted my ability to do the research required, and I've been able to maintain qantas platinum. I also wasn't sure about the transition period, but I've been flying business 90% of the time so transition probably doesn't matter.
On why switch, As best I understand:
AA points are much more valuable and usable. I already have some AA points. for example: being able to get multi-flight business for Australian domestic for 20000 points (flat fee) and $60 for 4, 6 months before flight time.
BA is have better benefits for their platinum equivalent. They also have an attainable life time platinum level. I think I've heard avios are also easier to get redemptions than Qantas. But not sure about that last one.