I think parlay is not for people who play it safe, if you do a parlay but the odds are still small, by playing safe like over 0.5 goals, then it's not a good thing. because the risk won't be equal to the profit you will get, at least I will parlay the odds around @5 and above, it will be better.
Parlay would be ideal for those who are risk takers and not those who play safe. Its the confidence that makes people bet parlays and if lucky win them. If your go for the higher number of bets in a parlay you are making it more prone to losses without any doubt. So a 5bet parlay can have a significant loss if you lose even just 2 of them.
Most gamblers like the risk though so they would without thinking anything more bet on those games that they feel confident about.
Non-parlay, parlay and martingale systems actually have a high risk. Anyone who starts gambling means they are ready to take risks, whatever system they use. And for me parlay are indeed quite ideal for gambling, but keep in mind that parlay will not be ideal with a high level because gambling will be more difficult than trading.
I myself usually use the parlay system up to level 2 only, when reaching level 2 I will return to the initial level and so on. Gambling is not a trade and the risk of gambling is far greater than trading so if you want to find it safe it is better to use a parlay system up to level 2 only.