When I started to work for my living, the basic rate of income tax was 33%. The basic rate now is 20%. There was no VAT, but Purchase Tax on luxury items, such as diamond jewellery, was very high. Successive governments have reduced the most familiar, best-known forms of taxation, clearly with a view to seeming like the nice guys who should be re-elected, plus reducing other taxes that usually only clock in for the wealthier in our society. Generally speaking, people have little idea of how much VAT they pay on many ordinary, non-luxury items, such as shoes for teenage boys still at school (they do have enormous feet) each year. Is it still at a rate of 20%? It was introduced at 5% and covered a much wider range of goods than Purchase Tax. Just for the record, bear in mind that there is a difference between zero-rated VAT (such as books) and non-VATable; the former can be changed on a nod of the head.
Of course, increasing the rate of income tax is shooting yourself in the foot if you are Chancellor of the Exchequer. It's much easier to blame other people for the shortfall of revenue to the Treasury.
In addition, it should be said, that plunging into wars is a hugely expensive business. I don't think we have ever had an account of how much the Iraq adventure cost, or, indeed, the Falklands adventure, or the Bosnia adventure or any of the others.