Because they need a safety valve in case it appears that the debt added to the deficit will exceed $1.5T. If it's projected to go above that, then taxpayers in the $50-$75K category are going to see their cuts evaporate. The great thing, is that it kicks in 2027, via the Byrd Rule, which will offset placing blame should those tax cuts expire. The drafters of this bill are still trying to convince us that the reason the corporate cuts are permanent, is the tired belief in trickle down economics. American businesses are making a killing, and have been for a very long time. The fact that business executives since 1982 have seen their wealth increase so dramatically, comparatively to the average American worker, highlights the fact that trickle down economics, doesn't benefit the workers of those companies. It's essentially a windfall for those businesses to pay themselves more.
So you don't think the wealth of those corporations has impacted the middle class? Where would the working class be working? Broke companies? Is your pension plan invested in broke companies? Should we eradicate the rich companies and base our economy on subsistence farming and cottage industry like much of the world? That would bring the classes closer.
I suppose you're right. There hasn't been any wealth trickling down. It isn't like our lower classes have a higher standard of living than most of the world's middle classes or something. And before you tell me how the wealth differential between the classes in America is, just remember how many amenities the average American below the poverty level enjoys that Andrew Carnegie never did.
The attack on "trickle down" isn't based on living standards or any measurable data, but on the jealous attitude that ALL the wealth should have trickled down. Thou shalt not covet.