(Most) Footballers come from a completely different demographic to (most) Tennis Players, Athletes or Rugby players and there are therefore, higher than average numbers of people who don't know how to behave in a decent fashion. It's not fashionable to admit it, but there are large communities in this country where what we consider a normal moral code does not exist. They have suddenly been given great privilege very early in life without being equipped to deal with it.
Tennis and Rugby stars have usually been used to privilege, even if not on the scale that comes after thier success and their upbringing equips them better to deal with it.
I'm afraid very large numbers of young men from the same side of the tracks as some of these footballers would behave in the same way given the chance. And yes, it is due to the parenting.
That said, the vast majority of footballers are decent young men who have worked hard for their success, do their charity work and support their families.
I would like to see the cubs take a harder line when their stars let them(selves) down though, but fully understand the financial reasons why they don't. It's a business after all. Where I work, drink driving is a sackable offence, but the top performing salesmen never get sacked for it, only those the company wants to get rid of anyway. Same thing.