This is likely an open question. I'm not an expert, but I'd imagine the main reason (at least our) cells all contain genetic code for the whole organism, is la

This is likely an open question. I'm not an expert, but I'd imagine the main reason (at least our) cells all contain genetic code for the whole organism, is largely because stem cells contain genetic code for the whole organism. If stem cells didn't have genetic code for say, both heart cells and lung cells, then it couldn't turn into those types of cells. And since all cells, stem from stem cells... then they also end up with the genetic code for the whole organism. Additionally, DNA is regularly used for creating proteins a cell needs for various purposes. Having extra genetic material than necessary, probably provides some benefits in terms of robustness. Like imaginably when a cell is exposed to a toxic substance, and has genetic code (recipe) for a protein that can neutralize it. Maybe 99% of the time it never needs that genetic code, nor is unnecessary to the cells particular function, but having it around can be beneficial in those rare circumstances. So is it wasteful and bad? Perhaps, but it likely also comes with some positive tradeoffs.