I get that, but they haven't actually arrived at zero. They've arrived at their version of zero, and thus have incentive to get to actual zero, since they're already at "zero".
Maintaining "net zero" takes a lot of work/money. It's not something you can do once. Every time you put carbon into the atmosphere, you have to go buy an offset. Over time those offsets get more expensive.
Wouldn't they be cheaper as businesses invest to use less carbon over time.
Like I said, low hanging fruit goes first. Later efficiency gains will be more expensive.