what is the value of mlflow nested runs?

What is the value of nested runs in mlflow? I thought it would be that a child run inherits params of the parent, but I dont see that

with mlflow.start_run(run_name='myrun'):
    mlflow.log_param('kl', '0p0')
    mlflow.log_param('name', 'ios')
    mlflow.log_metric('mu', 1.0)
    with mlflow.start_run(run_name='myrun2', nested=True):
        mlflow.log_param('name', 'weighted')        
        mlflow.log_metric('mu', 2.0)

if I collect the run info in python

df = mlflow.search_runs()

then we have

df['params.kl']

giving

0    None
1     0p0
Name: params.kl, dtype: object