Not entirely true.
In some countries (UK, NZ) Uber has to give you the price of the journey up front. Whereas taxis are metered and do not.
Uber UK has competition in thin regard with Minicabs, but the minicab apps are still shit.
Capped costs for consumers is a competitive advantage over taxis, and Uber has managed to find the sweet spot between hailing a taxi, and booking a minicab.
I doubt it’s /just/ smoke ventilation. Sure, it’s primarily there for fire safety.
But it probably provides ambient ventilation for the tunnel too. Tunnels with trains get hot. Most things, living or inanimate don’t like heat.
And if it’s always ventilating, it’s also might be expelling brake and metal dust from passing trains.
But all speculation. I’m not a train engineer, so I’m probably wrong.