That's the point. A battery is way cheaper and so would be the replacement, if not for the glue. If you are fine with it, thats fine for you.
And every solid laptop will need a new battery at some point. That all adds up to Apples revenue.
How much profit do you think Apple makes from selling batteries and replacement services considering how relatively few Macs Apple sells and how often people upgrade?
That's the point. A battery is way cheaper and so would be the replacement, if not for the glue. If you are fine with it, thats fine for you.
And every solid laptop will need a new battery at some point. That all adds up to Apples revenue.