Meh, I have Bosch, Ryobi, DeWalt, Ego, Ridgid. Why not just by the best according to cost/benefit for each thing. Corporate loyalty is dumb. I get the battery thing, but I'm pretty sure I got most of the tools at a good enough price to make the different batteries irrelevant.
Not all my tools are battery operated, corded jigsaw, sander, miter saw, table saw, etc. Not all the batteries hold the same purpose and would need a different charger either way. An electric drill and leaf blower need entirely different levels of power. In the grand scheme of things I think I only overlapped charging systems once.
I don't have many tools (or any children) but if I'm buying a bunch of battery operated stuff, you can be sure it's all going to be able to use the same batteries and chargers.
I’m sure you’re right and it wouldn’t be an issue, but I’m anal about reducing redundancy and complication wherever I can. If I can have one place to charge everything and don’t have to check what belongs to what, I’ll do it.