They don&#x27;t. They run them to make a profit off the spread.<p>The purpose of order internalization is to trade against uninformed participants (Joe 401k), without risk of accidentally trading against bigger informed players (Bill Ackman). If you are trading against uninformed players, your risk is lower and you need to offer a better price to get order flow.<p>Read these two blog posts for a bit more detail on price discrimination on the basis of delta toxicity (albeit not in the order internalization context).<p><a href="https:&#x2F;&#x2F;www.chrisstucchio.com&#x2F;blog&#x2F;2014&#x2F;fervent_defense_of_frontrunning_hfts.html" rel="nofollow">https:&#x2F;&#x2F;www.chrisstucchio.com&#x2F;blog&#x2F;2014&#x2F;fervent_defense_of_f...</a><p><a href="https:&#x2F;&#x2F;www.chrisstucchio.com&#x2F;blog&#x2F;2014&#x2F;mark_cubans_hft_idiocy.html" rel="nofollow">https:&#x2F;&#x2F;www.chrisstucchio.com&#x2F;blog&#x2F;2014&#x2F;mark_cubans_hft_idio...</a><p>If you want to argue that something nefarious is going on, go ahead and describe the mechanism. But whatever it is, it&#x27;s almost certainly not the mechanism chollida described.