>Why should we care whether they are making a profit or not?

Because it is generally in everyone's best interest for companies to invest in themselves rather than increase margin at all costs. Growth is good. Many companies would simply go under if you tax them on revenue.

>There are so many ways a company can legally and artificially lower its profit numbers

Then you try to cut those off as much as possible. Like most things in the real world, there's no perfect solution, but we weigh the pros and cons and make a decision.

> Growth is good

Given our current economic situation and our effect on our environment I'm not convinced that it is that simple.

Well it's not of course, and you're right in a way. It's also not good for a whole host of low margin / capital heavy businesses to tank.