"The past is the key to the future". If you have 20-40 years of saving ahead of, look at what happened in consumer tax law the past 20-40 years. The first public deferred income savings just began in 1980 only 36 years ago. 401Ks became common in the 1990s about 25 years ago. Roths only this century. Capital gains taxes were lower than income taxes 1977-86 and 1994 to now. The tax free home gains deduction started in the late 90s.
The point is that retirement tax vehicles changed a lot in recent decades making it quite likely they always will in the future. Take advantage what you can now.
But weren't all of these vehicles put in place by the baby boomer generation? And said generation will be retiring more and more in the future and also living longer. This would seem to mean that those people will be moving their retirement money from stocks to bonds or withdrawing it completely. Would this not require an equal amount of investors to take their place? Additionally, if this generation of baby boomers lives longer and runs out of money, is it naive to think that some kind new laws would be required to support them in old age?
Boomers were never fully in the self-savings pipeline since these savings accounts were only available mid way through their careers. Your point is more valid for GenX which is the first group fully expected to save for themselves.
The point is that retirement tax vehicles changed a lot in recent decades making it quite likely they always will in the future. Take advantage what you can now.