While I agree with you in principle, in practice it's not as easy as it might seem to ban second incomes. What if an MP is also an author? Do you prevent them from getting royalties from books which might have been written before they were elected? An MP I knew was a farmer - should he have been forced to sell his farm, which had been in his family for generations? There are MPs who are doctors; indeed, at least one MP worked as a doctor during the pandemic; should she have been banned from working?There are against using your parliamentary office to tout for business, but not for getting second, third incomes.
Having said that, the rules clearly need to be tightened.

