In my MHRP game, the PCs needed to go from Washington, DC to Tokyo. One of the PCs was War Machine. He commandeered a Stark Corp jet, and the PCs flew in it to Tokyo. The narration was along the lines of "You fly to Tokyo". My guess is that's probably a 12-ish hour flight, but we didn't both to Google it and find out. It didn't matter.
(I Googled it now. Apparently it's 14 hours.)
Nor did we worry about the time taken to get from the airport to the Tokyo skyscraper the PCs needed to infiltrate.
In my Prince Valiant game, the PCs travelled by boat from Britain to France; across country to Marseilles; by ship from Marseilles to Sicily; by ship from Sicily to Dalmatia; overland from Dalmatia to Constantinople. We didn't worry about how long this took. Obviously "many weeks" is the answer, but whether that's 3 months or a year didn't matter. What mattered was the various things that happened during the journey.
I get what you're saying. And that's totally fair. However, there are times when the speed of travel and the time to get from A to B can actually matter. Without any guidelines at all in the game, the players can't really come up with any sort of informed decision without negotiating with the DM first. Which is fine, but, that's the trade off.
How long does it take to travel from Baldur's Gate to Waterdeep is not an unreasonable question for the DMG to answer. At least in broad strokes.
Now, to be 100% fair, when I ran my recent Candlekeep game, every time I needed to look up travel times on the Sword Coast, I referenced
Forgotten Realms (Sword Coast) Interactive Map - The Forgotten Realms Interactive Map. So there are some solid arguments to be made that perhaps the core rules don't actually need detailed travel information. OTOH, not everyone plays in Forgotten Realms. How long does it take to travel between two cities in Ghaelspad (Scarred Lands Setting) needs to be answered somewhere.
But, we keep getting bogged down by the examples. It's not that there aren't rules for shovels, or tents or travel specifically. It's that there are no rules in general. It's all, "Ask your DM". Unless, of course, it's spells, in which case it's "Your DM will ask you how long it takes."
Which, in my mind, is the heart of the problem.