But 80x16 = 1280 diodes. If we skips the SIPO and uses his processor pins to drive them, he would need 160 processor output pins to get down to a 8:1 multiplexing ratio. Don't you see the problem. This really is not a CRT. You really do not run the diodes at us timing. The diodes can't run at infinite pulse quotas so you must, must, must run many diodes at a time. And if you do not use external latches to get enough output pins, then you need a processor with a huge number of pins.

In the end, you only have to alternatives:
- Run few diodes at huge multiplexing ratios. After adjusting for max pulse current, this would mean a very dim sign.
- Run many diodes at a time - possibly all the way to a fully DC-driven sign. But that requires either a processor with a huge number of output pins, or it requires a bus expansion. The best bus expansion there can ever be when it comes to number of output pins in relation to number of controlling pins is a SIPO. And if you think one SIPO chain gets too long, you may use two. Or tree. Or four. Or 32. Or whatever. But a 32-chain SIPO solution would still only need 32 data lines, one clock line, one latch line and possibly one outout-enable line - unless you instead let the row-drive lines handle the output-enable.

I can get an ARM chip with many hundred pins - but would you like to try to create a PCB where you route several hundred signals in trhough the very regular LED matrix with a minimum distance available between each LED?

Display manufacturers are not incompetent. They have spent time looking at alternatives. They have spent years and years and years considering different alternatives to make the optimum design. You, on the other hand writes answers without even considering earlier posts in this thread which means that you regularly returns to the same direct physical errors.

Yes, running a diode at an almost infinite pulse quota is a physical error. The multiplexing factor is a hard design limitation you can't get past. So don't think display manufacturers are stupid because they realize that they must drive many diodes at a time.

Yes, heat disipation in driver chips do represent a physical limitation in a design, so don't think display manufacturers are stupid if they base their designs on limitations specified in the datasheets of the used driver chips.

Yes, physical dimensions of chips together with the minimum required outlines on the PCB for maximum solderability are limitations that a display manufacturer has to think about. They are not stupid for figuring out that some constructs you have suggested to not fit.

A design manufacturer that controls the overall intensity of a huge display wit a couple of source code lines instead of having multiple driver outputs for each pixel isn't stupid. He has already noticed that your suggestion would result in a sign he can't sell because it would be too expensive. And he would still need proper instensity control since 0, 1, 2, 3 or 4 diodes in on/off configuration would represent too few intensity steps in relation to the ambient light.

And if the CPU is fast enough to build and output bitmaps for four times as many bitmaps, the manufacturer isn't stupid for thinking that maybe he can "over-scan" his display instead if he wants individual intensity in different pixels - still without the extra cost of multiple output lines.

The problem here is a huge gap between theory and practice. And when practical solutions implementations don't go for your theoretical ideas, you think that the manufacturers are stupid for not considering all alternatives. But don't you think you should consider the alternatives that are actually used in real displays. Possibly consider exactly why the sign manufacturer did choise a specific solution. Maybe the sign manufacturer did see one or more advantages that you still haven't opened your eyes to?