Death and taxes - or maybe not taxes

This seems extraordinary to me. The Public Accounts Committee report on self assessment for income tax states:

"HM Revenue and Customs collects £16 billion a year from Income Tax Self Assessment and sends Income Tax Self Assessment forms to around 10 million taxpayers. The Department achieved its Public Service Agreement target of 90.6% of 2003–04 tax returns filed on time by the 31 January 2005 deadline.
It has a target to increase this to 93% by January 2008.
As at July 2004 some £1.1 billion of income tax was outstanding from 1.1 million overdue returns. Similarly in July 2005 around 1.1 million returns were overdue, some 240,000 taxpayers had two or more tax returns outstanding, and 10,000 had six returns outstanding."

10,000 people had six years of returns outstanding? What is HMRC doing? God knows, they have sufficient legal sanctions to enforce compliance. Why don't they chase them up? As one of the idiots who submits his annual return in good time, why do I bother?