This should go without saying. Keeping a clean licence shows potential insurers that you follow the highway code and are (potentially) a safe driver.
On the other hand, points on your driving licence show the exact opposite. It follows that insurers will increase the premiums of drivers with points on their licence to offset the increased risk of claims involving these drivers.
This is especially the case with young and inexperienced drivers.The statistics show that young & inexperienced drivers are more likely than their older more experienced counterparts to be involved in car accidents.
If a young/inexperienced driver shows a disregard for the highway code and other road users it is even more likely that that driver will be involved in an accident.
Insurers are well within their rights to raise premiums to match the risk.