Why Does Lumbar Support Feel So Good?

Why does lumbar support feel so good? And what does it mean?
Is my core weak or what is the underlying issue?

I also just developed a small amount of scoliosis and my spine is missing healthy curvature (in lumbar and thoracic).

Thanks to TNation and the people who use it (I could name a few) my old sciatica issues have basically diminished. It was caused by (my hypothesis after seeing every kind of specialist and doctor) my straightened lumber pushing my pelvic forward (causing posterior pelvic tilt) and unnatural straightening of my lumbar compressed a disk which compressed the nerve and I had terrible sciatic pains.

Not really sure what I should be doing now. I think my spine is pretty stiff (and unnaturally twisted and not curved in other parts) and most mobility exercises feel pretty good. I do some yoga-type stretches, hip and Kossack-type exercises, and some core stuff.

Any thoughts or recommendations are appreciated.