Good to see Wawrinka plays more frequently again. Similar to Murray there was a relatively short phase in his career where he played outstanding tennis. Most of the other time it was a more of an up and down for him. In some games his fighting spirit was out of this world and he didn't give up a single ball. Now he is also injured more often and I guess he is trying to improve his cash balance a bit before he retires. He is going to turn 38 in March this year. It seems that after his retirement there is no other active tennis player from Switzerland in the higher ATP rankings.
Wawrinka got a couple of good years, mainly between 2014 and 2016 where he won 3 grandslams and played really great tennis. I think he more has a love for the game than that he wants to improve his cash balance as he won more than 32 million $ in prize money.
It says that he even won 35.5 million $ in prize money, but it is also a question of lifestyle. Guys like Federer don't need to worry about money ever again, but I don't know whether Wawrinka has any big sponsoring contracts like the other three guys. If you deduct all the cost for traveling and coaching and so on and so forth, 35.5 million sounds huge but it can still be spent. Wawrinka is more dependent on what he can earn now than what comes after he ends his career. Though I think that he is quite a down to earth guy but who knows.
He is still fun to watch though as he can be a strong fighter on the court. I'd like to see him advance to the next round and get a stronger opponent. Would he meet Zverev if he makes it to the next round?