Two friends take two different rides home from the same bar: one in an Uber, one in a traditional yellow cab. One app prompts a 20% tip screen before the ride even ends; the meter in the cab just shows a final number. Both drivers did essentially the same job.
Why the expectation has split
Rideshare apps built in-app tipping directly into the payment flow from early on, normalising 15-20% the same way a restaurant bill would. Traditional metered taxis, run under older regulatory and payment systems in most cities, never built that prompt in, so the norm settled on simple rounding instead — even though the actual driving and effort involved can be identical.
What this looks like in practice
Uber, Lyft and similar apps in the US: 15-20% is now treated as standard, not exceptional.
Traditional taxis in the US and most other countries: rounding the metered fare up to a convenient number covers it.
Airport taxi queues in many countries: exact fare, no tip, is completely normal.
Long rides, extra stops, or help with heavy luggage: a reasonable case for tipping above the baseline regardless of which type of ride it is.
International note: in countries where restaurant tipping is not customary — Japan, South Korea, much of Southeast Asia — that same norm usually extends to taxis and rideshare too. The underlying culture, not the app you booked through, is still the better guide.