It carries advertising. It makes several assertions: you'll be hard pressed to find commercial growers chitting, for example. Really, how do we know that? But if that's true, why should allotmenteers? It suggests recycling egg boxes for chitting, which is what I do, but also tells you it's possible to use seed trees, or even (ffs) wooden chitting trays, and gives links to sites that will sell you these commodities, both at Suttons Seeds, (though I notice the wooden chitting trays send you to a not-found page, perhaps no one was foolish enough to buy them). The site is said to be in association with allotmenteer.co.uk, the dead blog of a failed allotmenteer.
Next result from google is an archived page from the BBC. It tells you how to chit, but not why. And the BBC comes 3rd, too, in effect, with this result at Gardeners World, which has a video of Monty Don who opines that chitting, in effect, 'ages' the seed potato, thereby speeding up the process of growing. Hmm. Can't expect refs from a telly programme, I suppose, but Monty Don should know his arsehole from Christmas when it comes to potatoes, shouldn't he?
Getting Google to put its mortar board on and get some actual research in Scholar brings us to Wilson et al, 1998, which is a quantitative analysis of aspects of agricultural potato production. "Producers who chit seed potatoes are more inefficient than those who do not (although the estimated coefficient is not statistically significant at normal (small) levels of significance). This result is contrary to intuition and suggests that the extra labour and/or contract costs that this process necessitates may not be commensurate with higher levels of output." QED.
Putting this into allotment terms, you might be better off using the time and space you put into chitting for something else. However: it's marginal, so if it feels good, do it.
Wilson, P., Hadley, D., Ramsden, S., & Kaltsas, I. (1998). Measuring and explaining technical efficiency in UK potato production. Journal of Agricultural Economics, 49(3), 294-305.