I've always built up my bankroll by playing freerolls and cheap buy-ins. If you play well enough, you can do it. Slow and steady.--- It always helps to learn how to play well and just keep at it.
It's certainly possible to win a lot of money via the slow and steady route. Even if you just by play freerolls, if you can average $3 per day, that's over $1,000 in a year.
That said, I suspect some people fall into a kind of mental trap. $1,000 a year (or whatever other amount) may seem like decent money to them, but they neglect to consider the amount of time it took them to win it.
The trap is two-pronged. Let's say they played 300 hours and made $3.33 per hour. Someone who has the game to average that much from freerolls would have made more playing buyins.
On the other hand, I've seen people patting themselves on the back for winning a few hundred or $1000, who probably did so winning $1 an hour or less. Those people tend to see the total and not their per-hour rate.