It can be very helpful if it's done efficiently and with the end-user in mind. As you alluded to, there are a number of reasons people don't file: The tax code is too complicated, they don't owe money so they don't immediately understand that by filing they would be able to get some government support, they have not been filing and they're afraid that they might owe money so they don't, or they're just too caught up in the pressures of getting through the day-to-day to actually wrap their head around a complicated system.
There are all those federal benefits that are tied to filing and getting CRA to give them their notice of assessment so they can actually get their benefits. They're leaving a whole bunch of money on the table, money that they have a right to. There are things like the RRSP and TFSA for middle-class and upper-class people, but for low-income people, they need that notice of assessment to get benefits that would actually help them make ends meet and live a decent life. It can make a huge difference.