I don't think it's necessarily about hard work - a lot of students complain that they worked hard (and I don't doubt that they do), but that doesn't mean that they will (or should) get higher grades than those who don't. If I am hiring anyone from any discipline) I would prefer to have one who gets results than one who works really hard but doesn't quite cut it.
I agree that there are far more Firsts than before though, and also that the high numbers devalue the grade. I think that the honours system needs an overhaul, to be honest. Ten percentage points between grades means that someone could easily be two percent lower from someone who got a grade higher, but eight percent higher than someone with a grade lower. The 2% means missing out on a First (or 2:1), but there is no recognition of the 8%.
Also, some universities 'round up' individual marks, so that the final grade is significantly higher than it would otherwise have been (eg someone getting 68% on six modules would get each one rounded up to 70, so be eight percentage points up on the year - multiply that by three years, and there is a huge discrepancy), whereas others put in the actual grades awarded then round up the total, so get far less leeway.
I think it would be fairer if the actual marks were on the certificates, or if we moved away from having only 4 'bands' for UG and 3 for PG, although the HEAR certificates that are now given to all graduates would go some way towards that if employers knew about them, which I don't know if many do.