Because the servers ran on RHEL 6, so the application had to run on python 2.6. Servers will be upgraded to RHEL 7, so the application had to run on python 2.7

Because the servers ran on RHEL 6, so the application had to run on python 2.6. Servers will be upgraded to RHEL 7, so the application had to run on python 2.7 too in prevision of the upgrade very soon. Then servers will be upgraded to RHEL 8 maybe 5-10 years later, so the application better work on python 3 too. It is not glamorous but it's the practical way to make critical software work and continue working for some period of time. I think we can all agree that we don't want our banks to break every 3 months accidentally due to the newer release of whatever.