Not just web browsers, Acrobat (and probably other PDF readers) have supported executing Javascript in PDFs for decades.
I see from time to time that younger generations reinvent/rediscover the wheel and I chuckle.
I first met an interactive PDF when filing a form for some state matter (I live in Italy).
I thought that it was over-engineered and dangerous.
Also, this kind of things tend to gratuitously exclude non-mainstream (especially free) software.