Will you sit in the first class coach with a normal ticket

Every morning in the fastest train, full of people stand in the connection and coach. But most of time there are quite a lot vacant seats in first class coach.
Some people might walk in and sit down. Most of people might not, they are aware that they hold a normal ticket, even they know that nobody will check this during the journey.
I don’t like to say who is wrong who is right, I think it mainly depends on what you think you should do yourself.
It is not correct based on the first capital service rule, but why this company provide so many first class seats, even not many people want to use it.