The simple answer is because it was woefully underfunded in the past and attempts are being made to correct that. The citizens and settled residents of the UK don't wish to see their taxes being sidelined to subsidise the bureaucracy and administration of a migrant worker program for people who are seeking betterment in their lives. If they want to live and work in the UK and enjoy its benefits, that's great but it's unreasonable to expect the cost of the system that affords them that privilege to be supported by their hosts. The entire administrative costs of the migrant worker system should always have been treated and held accountable as a
profit centre for the benefit of the UK, with the costs of the system being passed on to the user.
I fear I may have just instigated the longest discussion in the history of this bulletin board!