Unfortunately, as Crackle says, we live in a litigious society. There's already been one incident just before this Giro, where one pro tweeted a comment (which by all accounts was well received in the peloton) about an Astana and was threatened with the lawyers.
Also, unfortunately, many of the commentators are drawn from the ranks of ex-pros and cycling fans and often do not want to acknowledge the possibility of cheating, do not want to raise that particular spectre (or should that be S.P.E.C.T.R.E.) when commentating, used themselves to 'prepare', don't see anything wrong with it, don't want to put the casual audience - who they rely on to sell advertising - off by suggesting the race might not be honest, etc. etc. etc.
Personally I think they'd be doing cycling a service by bringing things out into the open, but I don't see it happening.
Welcome to the forum, by the way. If you're sticking around, you should probably have a go at
@Marmion 's Pro Tour Punditry and show your learning by getting it as badly wrong as the rest of us.