They do not work because they're forbidden by law. It's a criminal offence to give work to any of these unregulated migrants. They're also housed by the UK government because it's a criminal offence to rent or sell them a property. Also they are often housed in the criminally unsafe (yes, that's also a thing) conditions and sometimes fed the mouldy food.
Imagine complaining about that (audible eyeroll).
So you want the UK to stop feeding and housing them but I guess keeping the laws forbidding them from working and renting? Why don't you and your mates don't do something about that already? Oh I know, last time they tried some ended up in prison for trying to kill the immigrants.
Mugrants arriving by boats because increasingly unhinged and rightwing governments paid off by dark money linked to Kremlin (we remember the suppressed intelligence report on Russian interference in voting) cut the country from the EU and closed down ALL the legal routes of immigration. Arriving "illegally" is the only way for them to claim for asylum.
And the funny thing is, the vast majority of these applying for asylum get their claims approved because they genuinely qualify, it's that UK is not offering any legal routes to anyone except Ukrainians (white Christians, I bet that had no impact) and a very few Afghans (these pesky translators, working for our troops risking their life now have a gall to ask for help once we let the Taliban back).
Did you see the graph showing illegal migration numbers before and after the Brexit vote? I bet you wouldn't like that. Because previous UK could just hand them back to the French.
All in all this is a self inflicted wound on all levels.
With the additional cherry on top of the utter lie in your last sentence. Immigration is not a net drain. Immigrant taxpayers are a net GAIN, and a very significant one, while the British citizens are a net LOSS to the treasury.
If we deported all the Brits the country would be much better off
