You were lucky enough to move there in an interesting year. Boise saw record snowfall last week, and it is true that a city only plans for 'the norm'. When planning for the norm proves ineffective, only then will they invest in new plows. Every city has posted evacuation routes in case of emergencies. Those evacuation routes (often residential side-streets that are otherwise not often used) are always the first to be plowed. Then they move to main arteries, then busy residential arteries. In a bad storm, most other residential streets are ignored entirely.
I'm in Montana. Our past 5 winters have been some of the worst on record. The first one was a nightmare; nothing was plowed. The plows the city did have were being run 24 hours a day on shifts, they were breaking down, etc... the breaking point was that they couldn't keep up with clearing evac routes. Over the next few years, our city has gotten VERY good at plowing. We have some seriously behemoth machines. Plows travel in pairs so they can clear an entire street in one pass, they usually run from 9 PM to 6 AM to not interrupt traffic and only spot check during the day. You almost never see them and the streets are always clear. It's amazing how far they've come. This winter has been nuts so far. Shovel 12" off the drive, shovel 10" the next day, then the wind picks up and drifts, so you shovel another 12" of wind packed ice. Rinse repeat for 3 weeks. My brother has been running his 4-wheeler up and down streets charging people to clear driveways.
tl;dr: They're right. If Boise rarely sees over 4", it's hard to justify new equipment in the budget. Buy yourself a 4-wheeler with a plow and charge $50 to clear driveways. It'll pay for itself in a week.