ICOs

I keep reading and hearing about people’s issue with ICOs in that they think some of them are security offerings, which makes certain people skeptical of investing in them. Can someone explain this more to me? 
Why are ICOs seen as sketchy? For example, I read some commentary about two projects that use the Mimble Wimble protocol: Grin and Beam. The person I was reading said Grin is good because there was no ICO, but Beam is less trustworthy because it had an ICO. Is that accurate/fair? If yes or if not, why?