I've never paid more attention than absolutely necessary to sentencing so my detail is a bit thin, but I'm pretty sure that under the original scheme, something like losing a job was not intended to be a reason for not disqualifying but many magistrates' ignored that. To be fair to them, they regularly come into contact with fine defaulters who have lost their job.
Anyway, during the tidying up effected by the Road Trafffic Offenders Act, 1988, this was put on a proper footing, or so they thought. "Disqualification for repeated offences" AKA totting-up is covered under s35 and among a lot of other twiddly bits, and subsection (4)(b) says:
(4) No account is to be taken under subsection (1) above of any of the following circumstances—
...
(b) hardship, other than exceptional hardship,
....
http://www.legislation.gov.uk/ukpga/1988/53/section/35
That was a clear attempt to reduce the number of repeat offenders escaping a totting-up disqualification, but a nod's as good as wink and it's a rare learned friend who won't argue that any loss of a driving licence is exceptionally exceptional hardship. Not always successfully, of course, but it's the successes that are publicised and that's what reduces the deterrent effect when some people come to believe they can't touch you for it and others believe that the law is riddled with loopholes. When it comes to deterrence, image is more important than substance.