Actually the standing capacity would be a factor in the crazy world of Irish Rail customer services. According to Irish Rail, paying 40 euro for a return ticket does not "entitle" you to a seat.
Why anybody uses the Rosslare train service is beyond me. It is almost as if Irish Rail are deliberately trying to drive customers away. How hard can it be? A 29k is not a suitable train to use for a run of more than an hour.
The Sligo service used to be like the Rosslare service - 3 or 4 trains a day rattling around half empty except for one or two busy services. But in a outrageous attack of good sense, Irish Rail invested in platform lengthening and increasing the frequency and the result is a service that is very much more used and that provides a useful social service even if it does lose money. It is a pity that they are no longer in a position to do the same for Rosslare.