Why didn't Liu go up with Yang?

There may be many reasons why Liu Yifei and Yang Yang didn't follow up. The following are possible reasons:

1. They may have no further relationship, or their relationship may have cooled down.

They may have no time and opportunity to further develop their relationship because of other work or personal affairs.

There may be some unknown factors, such as personality incompatibility, or they don't have much in common outside movies or TV series.

Please note that this is just some guesses about the possible reasons. The actual situation may be more complicated, or there may be other factors at work.