Well when it comes to retirement in football it something that has to do with person interest, imagine being in the system for over 15years, barely having time for your family, friends, kids and not being able to do some stuffs, all these are thing that trigger retirement in football. There are some who would even retire at their late 20s. So I would say it all individual differences when it comes to retirement in football.
You're right though, but If you're actually into football for the passion, you most likely will want to retire base on age, except for the fact in a case of a critical health issues that arise, because football is a career for most players and they're there for the money and also for the entertainment so considering to quit football early due to you not having much time with your family, means considering to resign your job when it's not yet time or when you haven't put a retirement plans in place, and talking about having time with your family, some of them move with their wifes and children, whereas some aren't married yet they only have their girlfriends.
Every professional soccer player usually wants to play longer. Therefore, age is often a factor that can dampen their passion and force them to retire. Another reason is injury. Many soccer players end up retiring at a young age due to injuries that are difficult to recover from. However, there are also those who do so for family reasons and want to spend more time with their families. However, a player like Cristiano Ronaldo, with his high passion and love for soccer, truly commits to everything. He maintains his fitness and lifestyle well so he can play longer. And family matters don't even hinder him. He always takes his family with him whenever he moves from club to club. And I think Cristiano Ronaldo already has almost everything, like money and other things, so now he plays solely with a certain motivation and simply enjoys his time as a soccer player.