[xyzzy_plugh]

I will agree that conceptually logging can be much cheaper than tracing ever can, but in practice any semi-serious attempt at structured logging ends up looking very, very close to tracing. In fact I'd go so far as to say that the two are effectively interchangeable at a point. What you do with that information, whether you index it or build a graph, is up to you -- and that is where the cost creeps in.

Adding timestamps and UUIDs and an encoding is par for the course in logging these days, I don't think that is the right angle to criticize efficiency.

Tracing can be very cheap if you "simply" (and I'm glossing over a lot here) search for all messages in a liberal window matching each "span start" message and index the result sets. Offering a way to view results as a tree is just a bonus.

Of course, in practice this ends up meaning something completely different, and far costlier. Why that is I cannot fathom.