My Asian Pear tree was LOADED with fruit for the first time last year, with a harvest of dozens of pieces of beautiful fruit. This year I am not seeing a single piece of fruit set anywhere, despite that it was covered with flowers in the Spring. Why no fruit? Similarly, I have a 6 to 7 yr old Rainier Cherry tree that sets DOZENS and DOZENS of healthy-looking baby cherries each year on every branch, which then proceed to fall off so no fruit matures. Why?

Your cherry can't self pollinate, it needs another (non-Ranier) cherry tree to pollinate it.

Your pear may have the same problem. It may have found a friend last year that's no longer in the area or that is pollinating on a different schedule. Or the blossoms may have gotten hit by a frost (I have no idea what your weather was like last spring).

Fun fact: even though they can pollinate themselves, self-pollinating trees do better with another, compatible pollinator in the area.