It came with a very detailed book. And Commodore sold another even-more-detailed-yet-still-cheap book that was so complete that it even included a big fold-out schematic diagram of the motherboard.
Would I have preferred to be able to do DRAW CIRCLE 0, 1, 23 instead of a long series of POKEs? Sure, because I was a kid and wanted to do things the easy way.
But those POKEs taught you about bits vs. bytes, and how computer memory worked, and how bitmaps worked, and about raster, and optimizing for speed, and ML interrupts, and math, and concepts like XOR, and all the important parts of the computer.
The biggest change from the good old days is that one could truly hope to fully understand a machine. The C64 was a bit harder, but not impossible. But the Speccy was simple enough that a near-100% understanding was achievable. This feeling of full control is what we lost.
Or, do what my car from 2014 did: The manual came on a USB stick.
The problem isn't distribution, it's laziness and greed. Documentation takes time and money. It's seen as a cost by people who don't understand the benefits.