While U.S. pressure played a big role, the IAPI program was conceived, designed, and was just short of being finally implemented (falling years behind schedule) by the Harper government, which was gung ho for more border controls and traveler screening. Indeed, the Conservatives oft repeated promises that the program (much broader than eTA or even the IAPI) would improve interdiction and enforcement of things like fraudulent collection of EI or health care benefits, as well as enhancing enforcement of the PR Residency Obligation. And the program probably has moved the needle some in this regard. Whether it has been enough to justify its costs seems quite doubtful.
Costs and inconvenience loomed as the major disincentives, with business and tourist related interests strongly opposed due to an anticipated repressive effect on travel to Canada. I have not seen the numbers lately, but as I recall it does appear these fears were well founded. There have been other events and circumstances, however, which also influence how much business and tourist travel there is to Canada (although the withered loonie has helped to offset some of the factors discouraging travel to Canada; some are recently forecasting the loonie is due for a big rebound).
However, with a few other exceptions, the EU seems to be an outlier in the trends. Border controls have increased way beyond what I might have imagined a couple decades ago, and there is little sign of any serious opposition to a trend in which these controls continue to increase throughout much if not most of the world.
While the big picture still reflects preferences and privileges which tend to be largely (not entirely, but largely) in favour of those who are Euro-Anglo nationals (thus the continuing high value of a Canadian passport), the trend is toward a future in which socio-economic factors, with much more emphasis on the economic side factors, will largely determine who enjoys preference and privilege. This includes who will find it easier to travel from country to country going forward.
I do not like the direction I see things going. But I'm at an age, and in a condition, where it is not likely I will experience much of the Brave New World looming on our horizon. Not really disappointed about this. But afraid for my grandchildren and, if and when there are any, my great grandchildren. Yours too. All of them.