Because the british rail system is one of the oldest in the world. Whether through mismanagement or misfortune it has never been able to afford the lump sums to

Because the british rail system is one of the oldest in the world. Whether through mismanagement or misfortune it has never been able to afford the lump sums to significantly improve its infrastructure and is left with the more expensive (in the long run) option of continually patching over the aging pile of crap.