Somewhere around 1/3 of all that Canadians consume is imported, from refined hydrocarbons to food products to medicine to building materials  etc.  Almost all of it is priced in US$ at the transaction level. A weakening dollar represents an erosion in real income for all Canadians. A weak $CDN means Canadian manufacturing companies cannot import vital components and equipment to improve productivity in their processes. So, a low loonie simply disguises declining productivity leading to a crushing of competitiveness even while their export product attractiveness improves as the dollar falls. This is a road to nowhere.

As for oil prices, the $CDN value for better or worse is intimately linked to the price of oil, even though petroleum industry is only about 9% of GDP.   There is a strong correlation between oil price and $CDN.  The main reason the $CDN is not below $0.70 is from oil being above $50.00.  That and Trump being a nut makes the $CDN a hedge.