Slightly bias towards older people.
Stress. Not knowing what kind of call you're going to get next and it possibly being someone who's going to shout your ear off or take an hour to find a fridge with a specific feature can start to weigh you down.
No weekends and no support from mannagement
To move onto something more fulfilling and 'open', so I could further my career and do something genuinely enjoyable. Leaving behind abusive customers is also a strong motivator.