It's not cost cutting. It's planned obsolencense! No Battery Engineer in their right mind would save a few cents on a balancing circuit. It's such a standard, it's like saving buying a car and the tank is sealed shut with gasoline inside.

It may also be that the battery engineers didn't have the final say...

Yeah, that's what they said.

Legislation on e-waste, serviceability is extremely important to prevent this kind of preventable waste.

It's not only cutting costs, it could also increase sales of replacement batteries I guess?

Not assuming that is the reason, but it certainly seems like a "positive" side effect for manufacturers.

The battery on both of mine went out quickly after purchase and Dyson sent replacements at their cost.

Dyson is only a premium brand if you think so. Their products are, and have always been, garbage. It is a marketing company, not a premium household products company.

As another commenter here said, this is an obvious case of planned obsolescence.