Playtesting is a key activity during the development of a game. Any successful game runs playtests often to see how the people react to the game set in place.
Usually in games company, playtesting is an activity performed by designers and product manager. But when also the engineers spend 1 hour of their weeks speaking with the Players (or potential players) they can also understand a lot and improve things out a lot.
Playtesting should be weekly, it should stay in the calendar of everyone. Especially for games as a service.