I read that it's an American thing. Americans have dryer vents in the house that need to be regularly cleaned or they are a fire risk, while the rest of the world has a dryer lint compartment in the dryer, that also needs to be regularly cleaned or it's a fire risk. FYI so that nobody gets butthurt: I don't think either of this solution is better or worse, they are just different. This is no "muuuh America Bad Europe Good" comment.
Notable exception: dry/wash combos, they just rinse out the dryer lint with the next wash cycle
Edit: And both make sense respectively. Since in the US you mostly build with drywall, it's cheap and easy to add a vent for the dryer. In other parts of the world where they build concrete walls, it's not so easy, so if you choose to move your dryer room in the future it would be a pain in the ass when the dryer needs to be connected to a vent. So it's much more useful to collect the lint and water in the dryer than to vent it out of your building
My vent line needs to be cleaned regularly to clear lint.
Lint traps are not 100% effective and if you haven't checked your dryer vent for lint recently, you should. If the heat from the dryer builds up enough, the lint can very easily start a fire.
I had a dryer for a while that vented into the room. It didn't just spew damp air though. There was a condenser and collector tank for water that had to be emptied between runs.