You do understand that you then have to deal with LA, probably a revolt or too, most likely an unaccepted culture penalty and possibly have to convert the thing? + The fact that you have to win wars to get it, take AE, warexhaustion, and money hits.
Your thought here is way too simplistic.
Okay, assume any province I conquer starts with -75% LA (50% after conquest than +25% increase in LA to get rid of revolt risk). I'm still doing better by taking 5 base tax with a 75% reduction than 1 base tax with no reduction. Even if you throw in -33% unaccepted, and suppose a -0.05 autonomy reduction monthly, I'm losing out on money for only ~40 years, which is very little when the overall result is saving MP which is more valuable than money. You're also missing that conquest is twice as useful as development anyway - development makes you richer, conquest makes you richer and them poorer at the same time! Conversion is rarely a problem, AI can't win wars, AE got nerfed this patch, I can buy down war exhaustion instead of spending DIP on DIP development and still make a "profit", and money is essentially limitless.
As it stands, there is no reason to play tall unless you're role-playing or some such.