[joejev]

Why does it matter if the users are high income? Twitter can still serve ads to low income users.

[rulum]

Ads are there to convert (sell stuff). Low income users buy less stuff. Also less expensive stuff. Ads catering to high income users tend to budget more for ads because they can be more lax with cost per user acquisition - their product has the margin to support it. All this leads to more income for twitter.