GIS is a welfare cheque. OAS is an entitlement. There are a lot of voters who will turf any government who puts in a drastic cut.

Blame all previous federal governments for OAS being unfunded. They could have put a modest amount of general tax revenue into an OAS trust fund, but insist on leaving it as being paid out from current revenues, while engaging in foolish starve-future-governments actions like cut GST.

As to age 67, U.S. social security is already on the march to make the standard age 67, currently sitting at 65-1/2.