It's an issue which has been discussed and play with for years. Traditionally, the personal allowance rose every year, albeit not always enough to keep up with inflation, but, more recently the Tories froze it for a number of years and, perhaps rather surprisingly, the current Labour government then extended that freeze.
I would add that raising the personal allowance (thereby increasing the threshold below which one will pay no income tax at all) is not a particularly effective way of achieving what you would presumably like to be achieved, because it reduces the amount of tax one pays at one's highest marginal rate. As a result, higher paid people benefit quite a lot more (up to double the reduction in tax paid, with current rates) from an increase in personal allowance than do low-paid taxpayers.
