Ninna - trusts have many many non-tax reasons behind their use. It enables a giver to give to a person who may not be able to manage the money sensibly.
For example, you may wish to give money to a relative, but be reluctant to, because they are too young, too old, have a mental illness, have an abusive partner, or are spendthrift and wish to be protected.
A trust allows you to do this, because the trustees and not the beneficiary have control of the money, but it has to be used for the beneficiary.
Since 2006, anyone putting money into a trust in excess of the nil rate band for IHT (or cumulatively in excess looking at the past 7 years) has to pay a 20% tax up front. In addition the trust pays tax every 10 years.
Contrast this with an outright gift to an individual, where if the giver lives 7 years there is not tax to pay.
Therefore trusts do not automatically reduce inheritance tax.
The rich can reduce the amount of money they die with, because they have plenty of liquid assets to give away. Trusts are really a red herring in terms of IHT saving - they possibly make a person more likely to give away something because they know it will be spent 'properly', but they are a very useful way of, for example, allowing someone with two children, one of whom may be mentally ill/have a controlling partner, and the other not, to give to both of them equally.
Do you have a particular scenario that you are concerned about? I really wouldn't believe all you hear on the radio about inheritance tax.