I belive this is normal coz i've heard on one of my friend that some of the ICOs as of now don't prefer to advertis here at bitcointalk. I don't know bout the reason but as you observe some of their bounty campaigns are posted in Mediums right?. Maybe they are now using some alternative channels to market their ICO which will be bad for the bitcointalk bounty participants and also for the bitcointalk community i hope it's not about issue of reliability when it comes to promoting ICOS.
There are quite a few that don't view the forum as being a viable way to promote their ICO, I guess for them they see it as either too much effort or just that the target audience isn't great as it's a lot of spammers etc. Many now choose to do targeted advertising through facebook etc and I've yet to come across a coin advertised on facebook that hasn't had great success in their ICO.