Without a dedicated IT function, problems either get ignored until they turn serious or get handed to whoever in the office is most comfortable with technology. Neither lasts. Users stop reporting things, small issues quietly become big ones, and the person who picked it up has a day job of their own.
Microsoft 365 needs ongoing attention in particular. Licences need managing, permissions need reviewing, security alerts need someone to actually look at them, and configuration drifts over time. With nobody owning that, things go wrong in ways that are hard to spot until they matter.