Use whipping cream in mashed potato

Why using whipping cream in mashed potato better than milk?

I tried once by using UHT milk, but it doesn't taste as nice as whipping cream, when using UHT milk, it didn't strong enough to cover the smell of potato, whereas whipping cream serves well and gives better covering over the smell of potato, because whipping cream has strong and heavy blend yet is sweetened, it gives fabulous taste to mashed potato.