"The pound will tank just like it did after the referendum result. It will rally again. You never hear a word when it rallies!"
Your layman's understanding of currency markets seems to be that it's all a silly game where sometimes GBP goes down but will surely come back up and none of it has any RL effect anyway.
You are wrong.
Here is the graph of GBP/USD. As you can see, it was about 1.70 in 2014, then 1.50 right before the referendum and then dove off a cliff when the majority voted for Brexit. It rallied for a while when it looked like the UK got its act together but it's now back at 1.21.
The effects of this collapse of the currency are numerous and nothing short of catastrophic. GBP lost 25% of its value since Brexit referendum. This means 25% higher cost of oil & gas, which is a major cost item for companies as well as people. (If this price rise isn't being reflected directly to your bills, that difference is coming out of your taxes).
It also means that all your imports are now much more expensive, pushing prices up by 20-25% on everything imported into the UK. This affects not just your medicine and tomatoes, but also all materials used by UK industries, clothes you buy from India & Turkey, etc. It means your companies will struggle to make profits and cut costs (less investments, lay offs, etc) and try to raise their own prices, which will mean inflation for you, the consumer whose wages will not increase in line with these price hikes. That means you will be poorer.
"But the UK is no longer dependent on industrial production. Most of our economy is services", you would say if you knew this subject better. Brexit delivers an even harder blow to the financial services industry, which serves EU countries through passporting deals. Those will be void upon no-deal Brexit and those service companies will close UK operations or suffer massive revenue losses & job cuts.
As for the City - London surpassed NY some years ago and became the world's #1 financial center, on the back of its unique position of being an Anglophone, cosmopolitan EU city where all corporations as well as banks liked to base their EU headquarters. London also enjoyed the position of EUR currency operations. That is no longer the case and we have already started seeing large scale layoffs as HQs are being moved to mainland Europe. Passporting problems will also severely affect UK banks and consulting services and you will see those companies shrink their London operations & personnel.
The fall in GBP is predicting these shocks to UK economy, and that even before the political ineptitude and uncertainty over N Ireland.
Those of us with zero understanding of all this fallout should educate themselves a little before declaring that all will be fine and GBP falling doesn't mean a thing.