Could Mrs. Elton possibly be alluding here to the taint of association with heavy industry and the slave trade? Here's a quote from the online archives of the City of Birmingham:

"Responsible for oppressing millions of Africans for an unjust profit, the transatlantic slave trade prospered in the late eighteenth century. Birmingham itself, a town at the centre of the industrial revolution, was far from untainted by this trade. Selling guns, engines, metals and a range of industrial products, its growth became linked to profits often made indirectly from the buying and selling of slaves. For example, we know that a proslavery petition was sent from Birmingham to Parliament in 1789 by those manufacturers who feared that the economy of the area would collapse without the 'African Trade'."

Ideas from those more in the know on historical matters?

In any case, it's clear that "my brother, Mr. Suckling (who has a BAROUCE LANDAU)" is barely a generation away from some non-land-owning activity, just like the unpromising Tupmans.