Japanese Tour director jobs would be a lot easier if they could pile everyone into a cart, stick a colored hat on them, and make them hold a rope. Or if their customers were so good at waiting patiently and carrying out their trash. I can only wistfully imagine being able to board & de-board a 40 person bus in less than 10 minutes

I'm not the tour person (my parents like traveling with a group of people who charter tours) but will say a good tour director does improve the trip experience and almost as magical as Mary Poppins. Some lean more towards being a bit of a concierge or fixer and have built up business relationships with the venues. Others are great teachers.

ETA: One of our tour directors in Japan discreetly tipped at specific ryokans which offered kaiseki meals & entertainment to maintain good business relationships. I only knew because I nosily asked about the corollary (high context) rules of Japanese tipping and she was a higher level dedicated guide for the tour operator. This was her obligation on behalf of the tour operator, not on behalf of the guests. Tourists really aren't expected to guesstimate a tip. If the hotel wants to add a specific % service charge, they'll typically say so on the reservation. Izakaya may also have a table fee-esque charge called otoshi and you get a small appetizer for the fee which will be stated on the receipt.

JTB (a large Japanese travel agency & tour operator) doesn't mention gratuities for their tour guides for tours marketed to overseas guests https://online.jtbusa.com/TourList.aspx

OP - you might be wondering what the Japanese do to show appreciation of great service. Give them more of your business. For a tour company, that may mean use them again and write corporate to say your guide was excellent. Some people will also specifically request tours with that guide on other itineraries (or charter). Americans also tend to like to give gifts but be aware that Japanese tend to view gift reciprocation and obligation quite seriously and it is something I personally try to steer clear of.