The main reason is the lower cost of playing football? Or is it different when we talk about Alberta or Toronto? Because Toronto has an MLS team.
There are a few factors.
1. While women's hockey has certainly taken off since the days of ringuette (which Mrs_NyQuil HAD to play as there was no girl's hockey back then), I wouldn't be surprised if the distribution is different between boys and girls. Anecdotally, I know a lot more girls who play soccer than guys.
2. Immigration is often cited as a powerful influence on the sports that kids play. Basketball in Canada in particular is driven by largely black populations in Montreal and Toronto. There is also the "Carter Effect" which led an entire generation of Canadians to take up the sport.
The Carter Effect - Wikipedia
Soccer is no different. I play in an adult league, and at least half the teams are cultural in nature (e.g. the Brazilian team, the Jamaican team, the Syrian team etc).
3. The cost of hockey has skyrocketed with leagues, tournaments and training now operating year-round and specialized forms of instruction evolving. Soccer is comparatively cheaper to play and one thing Canada has a lot of is land, so it's not hard to set up a lot of fields. Fieldhouses and domes are starting to crop up with increasing frequency to allow soccer in the winter, but that's still a major barrier to competitive soccer (outside of BC where the weather is milder).
4. As a result of its cost, as you pointed out, soccer is largely viewed as a participation sport in this country, meaning that a lot of people play it, but only for fun. We have very few coaches per capita licensed at the top level, meaning that while we have a lot of players, we don't have a lot of top quality instruction. Iceland is viewed as a model where they pushed through an initiative to vastly increase the number of qualified coaches. As it stands, a lot of coaches end up as one of the parents of one of the kids.
Canada should use Iceland's model for soccer success | Toronto Sun
5. Watching soccer is very popular in Canada. I think people would be surprised at how many people follow the EPL, and the big tournaments like the World Cup and Euro end up on all the televisions in bars. The MLS has made a dent in some of the major cities, but I'd be surprised to see if it was a major factor.
Alphonso Davies and the current crop of players could create a renaissance in Canadian soccer much like Vince Carter did in the early 2000s for basketball.