1. Stringent drug tests in Olympics. Performance enhancement drugs are banned.
2. Foreigners can't represent national teams in Olympics
3. Each and every country need to play qualifying tournament in Olympics, unlike the case in ICC World Cup where 80% of the teams gain automatic entry
4. The revenues will be shared with the respective national Olympic body and not with the cricket board
5. No special treatment for any of the teams. All are treated equally.
I am quite sure that all these reasons are the main cause why cricket is not going to be in the Olympics. The big 3 surely do not want to lose their control over the ICC and if cricket is inserted into the Olympics that will surely be a problem for them. they are a lot used to the special treatment by the ICC and if they are treated equally as all the other teams it will hurt their ego. So, even if ICC wants to add cricket to the Olympics I don't think the big 3 will let them.