This is the last time something on the account record in the database changes. Now that deposits has been separated, it will change even less frequently. It's not related to other details (like the allocated hash rate, as an example, which is calculated each time it's needed). I don't think there is any reason to update it more frequently.

What are the details on the profile page that you want to see updated more often? I'll check which is the refresh time of those details.

Maybe I'll also change the description of the "last update" entry.