Why in the eighties they did not squezed hw?

Mentality, taste and market: "we have thousands of Japanese kids playing RPGs, who cares about SHMUPs with smooth scroll?"
Even Space Manbow doesn't have it...

But there were plenty of shoot'em-ups on the NES, so clearly 'hardware' was an important factor here.

We have an advantage of some 30 years. Konami and others had to make games for a living. We've been spending years and oodles o' productions just to optimize scroll 'n logo demos. You know, copy scrolls, #18-scrolls, intertwined scrolls (one of those ANMA demos), stretching scrollers etc. etc. Yeah, you can count on it that eventually our scene-style handling of the Z80 and the VDP is more potent than the routines that commercial developers in the 80's used.

We would use bitmap coins in Usas, it's screen 5, no scrolling, plenty o' time, Konami used sprites. Heck, Konami used a genuine outline routine to draw those light glowing effects on those names in the SD Snatcher credits/cityscroll. We'd prolly just store such frames in mem and unpack them as needed.

Three decades, and different objectives, that's the difference.

I do not agree, instead. look at the speccy or c64... they have tryed the impossible to squeeze the impossibile. maybe if msx had a more diffusion they will increase the efforts... the same thing is for spectrum convertions

I don't think the developers maturity had that much to do with it. On both C64 and Speccy you don't have neither tiles nor direct access to VRAM, so if anyone need to scroll anything, they would move pixel by pixel, unless they wanted a really fast scroll effect to move more than a pixel row/column at a time. Neither of those had such thing as hardware-accelerated scrolling...

On the other side, the Texas Instruments VDP used on MSX is tile based and it doesn't allow direct vram access, so it's simpler to move a tile at a time when scrolling. It's actually easier to scroll on MSX1 (8 pixels at a time) than on Spectrum, so developers took a this matter lightly on MSX... And it also makes more sense that Japanese like RPG more than they like shmups...