Our experience, attention and functioning is affected by endless prameters (examples: expectations, framing, level of experiencing various aspects of a situation, etc.)
There are even more ways to manipulate experience and attention. Many of them quite effective when taken to the extreme. And various manipulations seem to lead into desirable ends.
Why not use all these tricks? (we already use some without thinking of with. But it sounds an open vault to improve life)
1) Management costs. Nothing happens on its own. It takes attention and actions (at least mental actions). We are not always rich in these. Sometimes attention is needed to more stressing needs.
2) Complexities. Every approach in life and the like is related and involved in a wide variety of activities and cognitions. It is not so obvious what other effects and shortages is created by every change of approach.