I think bank mergers and sluggish privatisation are two main factors contributing to the loss of banking jobs in the government sector. The public financial sector and finance businesses are being taken over by private sector banks, reducing the amount of work chances for hopefuls, as I see.
I thing following are the caused behind it:

Banks are merging: In order to run four stronger and bigger banks in India, ten Public Sector Undertaking banks were combined into four Public banks, reducing the number of Public banks from 27 to 12.

Economy has slowed down: GDP growth for the year is expected to reach 5% in 2020, according to the RBI and the government. According to recent statistics, there has been a significant drop in employment trends as a result of the economic slump.

Pandemic situation : COVID-19’s continued spreading across the country has destroyed the banking system, causing major instability in global markets.
Also I guess that because banks may be forced to work with a reduced staff even after the COVID situation to make up for the loss, the number of recruitment per year may be reduced.

AbhishekBharti changed the title to Why vacancies in banks are reducing these days .

Covid pandemic situation can be said as a major reason behind reducing vacancies in banking jobs. It hits national as well as global markets hardly and creates disturbance in the economy of many countries.