"The bike is about 25 years old and the bearings, gears, and chains are still the originals " Do tell. who is the manufacturer ?
No idea, that has all worn off. The bearings are sealed (no lubrication), wire cables to gears and brakes have had to be replaced. There would probably be some gain in efficiency with a new chain. However I primarily ride for exercise, quick errands and irritation avoidance (traffic lights, parking spaces) so don't mind if it is sub-optimal pedaling (spray on lube for longer rides). It is a low-end mountain bike so sturdier construction than a touring bike though I don't ride it off-road.
That is key, touring bikes sacrifice too much in strength to get the weight down. I don't want to ride fast, it makes near misses more frequent and more serious. Heavier construction keep wheels from getting out of true. The biggest issue is flat tires from roadway glass and blackberry thorns. I don't ride it in Tucson because of the tremendous sprawl, lack of bike lanes, geriatric drivers, and cholla thorns everywhere. Baskets front and back, though side paniers are really safer in keeping the center of gravity low with weight. Very dangerous to ride with a backpack.
People in this town will pull bike trailers, moving standard refrigerators and similar across town. I don't see a lot of Millennials ever purchasing a car. They are more urbanized to begin with and it is far cheaper to rent a car for the two week vacation than own one. I read somewhere that the average American male spends 30% of his lifetime income on car (resp. pickup) payments. Which accounts for zero net worth of so many people here.