Most people in Scotland, Wales and N Ireland fear we would be in deep trouble if we left. The scenario that alarms us is:
Recession - for a short while - a year or two at least, as predicted by vast majority of economists. (who often disagree, but not on this)
More austerity, reducing further the amount of funding we get from Westminster to run hospitals, schools etc.
Loss of regional funding from the EU - much of which is used to promote economic growth.
Loss of farm subsidies, which will mean loss of rural jobs - the farmers support a wide range of local businesses directly and indirectly related to farming. (The farmers are not believing Gove and Johnson when they "promise" that this money would not be lost. The are noting that extra money is being "promised" to the NHS and many other things. Farmers are not daft. On the map that Durhamjen posted yesterday one of the keenest counties to Remain was Ceredigion which is virtually all farms and not much else.
Many businesses are worried about their exports, whether it is farm trailers, whisky or lamb (a lot of mountain lamb goes to Spain etc)
Also
The N Irish don't want border controls reducing the flow of shoppers from the south and hampering their own freedom to nip back and fore over an open border, should they fancy visiting their aunty Maureen or having a weekend in Dublin.