You would be right to, if you hadn't designed the house to have only a very low heat requirement. MVHR does only move relatively small volumes of air, but if that is all the house needs, no problem. There are people living in places as diverse as Inverness and Penzance so there are significant variations in heating requirements due to climate, not often mentioned. There is not a single solution for all designs.
Fortunately, UFH is not the only way to heat a property, so it is comfortable. Before I built my low energy house, I too visited PHs that weren't comfortable, and they had UFH. It is not too onerous to meet the threshold criteria for a PH, but they can be bettered, reducing further the space heating requirement.