I have to suggest that indeed it does have to deal with a great expansion of the economy and more disposable income that necessitated more coinage. There are parallels in the USA during the time, when the large cents of 1793-1857 were minted they were never minted in quantities in more than 3-4 million per year, but that seemed to be sufficient for the times, but then when the small sized cents were minted beginning in 1857 they were minted in much larger quantities that were often 10 times the previous large cent size mintages. The early Victorian era saw an expansion of consumer spending on a scale not seen before, while it pales in comparison to today, then it was much more than say the Georgian era. Remember this was the era of the Great Exhibition of 1851, Britain and the United States were seeing their economies expanding on an unprecedented scale, the result was that much more coinage was necessitated.