Which is why lower consumer prices aren't a valid defence against anti=trust. Nor is the argument that markets "naturally" lead to monopolies or (at best) oligopolies and cartels - even though empirically they do. So much so that setting out to create a monopoly is a bullet point on many unicorn-wannabe business plans.
The problem is abuse of power without oversight.
YouTube can screw over content creators with its insane system of copyright strikes. PayPal and Amazon can keep legitimately earned money on the pretext of non-existent ToC violations. Apple can decide to bar you from the App Store on a whim and clean-room your best green shoots ideas into its own products. Google can decide that you earned too much in ad revenue and shut you down just because it can.
People have lost businesses and livelihoods because of these practices. The monopoly position held by these companies makes them unassailable.
That's what antitrust protection is really about.