They already do - it's no co-incidence which big corporates have managed to negotiate huge discounts in their tax bills.
Besides, not everyone is a tax expert, why should WE have to guide them ? For a vast majority of people their tax affairs are simple yet HMRC don't even get those cases...
One of the biggest issues is that HMRC doesn't even understand tax itself and is pretty poorly run. I struggle to believe they have the skill set to work out these schemes given it took them 7 attempts to agree just a single year of my tax liabilities ( as well as 18 letters from them and six...