Europe employs the PEGI system which is not strictly a requirement for grading games for content. We have 3+, 7+, 12+, 16+ and 18+ along with other symbols depicting content such as strong language, violence (even discrimination). The UK also employs the standard BBFC certificates that normally go with films such as U, 12, 15 and 18 (no PG) but again these are only just starting to become routine. Most games have either one or the other by means of classification.
As for the T rating for a poker styled game, I'm not really surprised. In the UK, you have to be 18 or over to be allowed to gamble (this includes casinos and fruit machines in bars and pubs). With that ruling I'm not particularly amazed a poker-sim is graded for Teens and above. Obviously, kids under this age range probably shouldn't be looking into concepts of gambling even if it is purely a simulation. Can you imagine the uproar the games company would get when kids around 8-10 years old are all suddenly playing Texas Hold Em in the playground fed with the usual excuse "I got the idea from a video game"! As I said...no surprises here...