Why are the peak periods not uniform across all public transport?

I was searching around for the definition of peak periods in Singapore and I found that they are very clearly defined for taxis but yet, not defined for our buses and MRT lines. I only found the following definition of peak periods:

Peak periods:

• Taxis: 6 - 930am Mon - Fri, 6pm - midnight every day
• MRT: 7am - 9 am
• Bus: Non-existent

Why the disparity? Is the peak period very different between Taxis, MRT and Buses in the same country? No they are not. The timing is where everyone expected frequency to be increased and yet we're always facing issues of getting our transport during those periods.

Since the taxi transport operators are charging more during peak periods, why are they not increasing the frequency for the MRT and Bus too? They are the same operators and there is no excuse for some of them because the trains are driverless.

Let's start by aligning all the peak periods between all our public transport systems, taxis, MRT and buses, after which we can then start to align all the service levels expected during those peak periods. I do not see the logic why taxis have different peak periods than the other transport systems.