Many SS amps are like that, but it's not some universal truth. There's all kinds of designs to make the poweramp behave more like tube amps do.
Plus it's not like tube amps are the same either. If I run my Mesa Mark V's preamp into my Fryette PS-100, it has a lot of the qualities you attach to solid-state. It feels more immediate and very in-your-face compared to running the Mark V into its own poweramp. Even within that MKV poweramp, whether you run it at half power, 10W single ended, with or without variac, with tube vs diode rectifier, triode vs pentode the feel of it changes noticeably.
I remember back when I had the Bogner Goldfinger 45 SL, I really would've loved if it allowed per-channel power scaling because the "low voltage" mode felt much better on the clean channel - more "bounce" and "sweetness" to it at the same settings and volume.