mortgage app and pension

can someone please explain to me why it is when applying for a mortgage we have been told they can not take my pension into consideration, it seems strange to me that they will take certain benefits into account but not a pension , benefits can change as circumstances change, my pension will always be my pension

would appreciate any advice on this

I will be 62 in September if that has any bearing
the mortgage will be for a 15 year term (partner is 50)

Regards
J
xxx