Why would my works IT guy think he can’t run data and voice over the WiFi?

I don’t do IT here so idk what they’re setup is like. They don’t have a lot of the kinds of tech they should (excel spreadsheet to manage orders/customers instead of a DB).

I was watching the do everything guy string some cat5 and asked why he was bothering if they have WiFi coverage. He said they can’t do data and voice over the WiFi.

I just wanted to know if there’s any good reason for this. They don’t need lots of bandwidth or anything. Just emails and web surfing mainly.

Edit: we have 6 people in the building with desks.