Rarely because of the operator. The usual causes are thick walls in old buildings, consumer equipment doing professional work and networks that grew piecemeal, with routers and repeaters added at random.
The consequences are well known: rooms at the end of the corridor with no signal, a connection that drops between the lobby and the bar, and receptionists acting as a helpdesk.
The fix always starts with measuring on site, in every room, how far the signal reaches and where it is lost. The network is designed from the real building.
More routers do not solve it. What solves it is a network designed by people who know hospitality.