Doing all the work twice is expensive. It’s not just the actual work of doing the design, but then you’re 2x testing costs too (unless you YOLO one of the modalities). More cost effective and better quality result to make a choice to make the platforms more uniform rather than trying to optimize for both. This obviously only holds when there’s a massive disparity in revenue. If your PC/laptop users make up a non-trivial parts of revenue it can start to make sense (but again, generally only if doing so will help you retain that market or get better revenues). The other thing unifying things does is it helps engineering and design teams by removing complexity.

All of the above is general trends of how these decisions are made. There will always be counter examples or situations those aren’t good ideas (or that someone has made a mistake applying a lesson to the wrong situation).

Saying an entire group of people is lazy or dumb is not a particularly insightful way of looking at anything that helps your understanding of the situation or learning what kind of results different incentives yield.