Why are there not as many IT companies in the outlier counties of Ireland?

Dublin is the only area of the country that could be classified as a city by the official standards population-wise. Cork almost was, but there weren't enough people. So to start off with, it already has a wide variety of people there which is useful. Dublin is the best in regards to transportation in Ireland and has been for years because of the river Liffey. It has good roads and a decent public transport system (which employees may rely on). If a company needed to buy materials from another company or a variety of companies in Ireland, it would be impractical to be so far away from them when they're all mainly in Dublin. UCD, DCU, Trinity (TCD) and a range of colleges are all in Dublin. This means that a lot of the top students and graduates in the country are living in the area. NUI Maynooth is also quite nearby. It's a short train ride from Dublin. It's late at night and I'm just home from work, so if I think of anything else I'll update this! I think top potential employees and transportation are the top reasons though.