It’s more a function of business reality; SMEs do not get the option of bespoke face to face negotiation and customer service; they get boilerplate documentation and a ratecard on a take it or leave it basis. Large corporates have marketing functions who need to(1) justify their existence, (2) be wined/dined/mollycoddled (3) ensure the full product suite is delivered to their mothership (delete as appropriate.
These latter functions have always been located where the large corporates and agencies are based and that is simply not Dublin. The billing and support functions for all clients will, I expect, always remain in Ireland as, in common with financial services, that is always what the service based FDI is all about in Ireland. I’m willing to venture, from cynical experience, that the long term tax take in the UK does not end up being that big. The large revenues will encourage large costs to be allocated to the UK.