Because they are widely ignored and/or silenced. There is no shortage of research out there that calls into question the safety and efficacy of vaccines. I suspect that you just haven't been looking.
The mechanisms for silencing dissent are well in play, very effectively.
The governments are involved. NGO's are involved. School systems are involved. Medical schools are involved. And the big money foundations are calling the shots. Uh, OK, bad pun.
Why are all the forces being brought to bear on forcing people to vaccinate their children?
Does anybody think it's because corporations love children?
Uh, well, how about government loves children, after maybe the 2nd trimester or whatever?
Want the real answer? Want to know what is really being done and why?
Here's the answer, in full.
https://www.youtube.com/watch?v=ek5vse2_Aq0