Why include a table of figures?

When I refer back to a thesis to find a piece of information, I find the lists of tables and figures to be extremely useful. I often have a general idea of what I am looking for. Turning that general idea into a simple text search that does not yield hundreds of hits is difficult. By reading the short captions in the list of figures, I can generally find the figure I want.

You appear to start from an assumption of reading on screen. If some actually wants to read a thesis (as opposed to looking something up in it) there's a fair chance they're working on paper. An examiner for example. A list of figures/list of tableswill help them track down some of the important material quickly.

If someone has a paper copy, good lists are really useful, but xcost a couple of pages

If someone has a PDF copy, the list costs them nothing. A few bytes of data, and there's no need to scroll past it as any decently-produced thesis PDF will allow you to click on the headings (or "Contents") in any decent PDF reader.

So even with primarily electronic distribution (which is an optimisitic assumption) these lists will benefit some of your readers, including some important ones.

I found them quite useful when checking the print copies -- text was easy to spot-check, but ensuring that the figures came out right was important.