Cogent speculation - but businesses use machines, not individual stamps. The general public only purchases stamps in volume for special mailings (Easter, Christmas & Valentines) and probably many are misplaced before the next occasion.
E-mail is taking over communications and the remaining letter writers are a dying breed. The only niche left are the philatelists.
Don’t see mass hoarding of ‘forever’ stamps - but it does make sense for the Post Office to curtail printing costs.
The post office spent many millions on magazine sorting machines that sit unused because the unions didn’t want to lose their jobs.