It’s not eliminating DST as such, it’s switching to a different time zone than their neighbor. Eliminating DST means that either the East-most or West-most country would get unfavorable hours, either in summer or winter. They can mitigate that by changing their time zone, but now that means they’ll be in a different time zone than their neighbor, which they previously shared a time zone with. For example Spain could switch to a different time zone than France, to get less extreme hours of days compared to what is currently Central European Time, but having a time difference would have economic costs between Spain and the rest of CET land. (Arguably, both Spain and France should switch to UTC, based on their proximity to the Greenwich meridian, but a time difference between France and Germany would be even worse.)

I’m not sure how real those costs would be beyond a transitional period, but that’s the discussions that have been going on. It’s a political risk, and nobody wants to be on the losing side of such a change.