Bytes currently in use not able to reach till maximum bytes configured


Recently our mongo reached 50% Ram utilization, so we decided to increase the infra. Earlier Mongo was running in 16 core 32GB ram, which we increased to 32 core 62GB ram.
But we noticed that this time Mongo was utilizing only 42-43% of Ram i.e. around 25GB.

With db.serverStatus().wiredTiger.cache we found that
“bytes currently in the cache” : 25984630208
“maximum bytes configured” : 32509001728

So is there any reason why Mongo is not able to utilize the maximum allotted ram, but instead is stuck around 25GB?