You need to appreciate not only that the courts are becoming more savvy about e disclosure and requiring it, but also that the implications of failing properly to preserve evidence are significant.
Arguably, a duty to preserve evidence arises once litigation is reasonably anticipated.
In the US there is a growing body of what is called "spoliation" litigation, where parties use the fact that the other side has not preserved evidence to strike out cases etc. In one case involving an investment bank, one party had so blatantly failed to preserve evidence that the judge directed the jury to find them guilty of conspiring to damage the claimant because of it.
There is the possibility of a case in the UK being struck out because parties have failed properly to comply with their duty to preserve and disclose evidence.
Even if the courts don't go that far, in a UK breach of copyright case in the mid-1980s, the court drew adverse inferences about a party's conduct because it failed properly to disclose documents when it came to deciding what losses had been suffered which had been caused by the breach of copyright.
A failure to appreciate what electronic disclosure exists, and to ensure it is preserved, can mean that a client would lose its case unnecessarily.