Making a thread is easy but maintaining it is the hard task that a project developer is assigned on.
But a project that don't have an ann thread doesn't mean they're bad and a scam project. It's either way for those that have their own ann thread, that doesn't mean they're a good project as well.
However, lets acknowledge the fact that crypto world is bigger than this forum as well, there are plenty of places that they list, such as twitter or reddit or whatever where they ignore bitcointalk and that is why they may not have any ann thread here as well. This is why I think it is all about if they know about it or not.
Most that I'm seeing are in Twitter and they're taking their community from there to their very own Telegram groups and that's the ugly side of it. Because as we know of these Telegram groups, that's the easiest place for scammers to stay.
Easy to add new members without their permission and most talks are being done quickly and can alter discussions and change names so fast.
But those that acknowledges the forum, they always include the forum with their announcement because of how they respect it and knew that i was started by the OG, satoshi himself.