IT department's don't like MS access for a variety of reasons. One is that MS access is not the most secure option. Another is that amateurs, often one of the bosses! Create MS access databases, get stuck, and take the unfinished product to the IT department expecting it to be sorted!
MS access is ideal for getting your project up and running, it is a very fast and easy development tool, ideal for a quick and dirty solution. If the quick and dirty solution becomes more permanent, more sensitive, then it is possible to upgrade your access database to MS SQL.
It is not uncommon to have twenty users using a MS access database, it depends on what they are doing.