It could be a matter of saving a few pounds or simply forgetting to follow up annual reminder but if you have a dog, cat or rabbit, please check out above article.
If you check out different vets, you will find a range of prices for vaccinations and other standard services. And PDSA is a charity offering free services for those eligible (who can choose to donate what they can afford)
Your pet deserves to be protected from serious diseases - I don't know the legal ins and outs but the animal welfare laws do place responsibility on owners to look after their animals.
If level of vaccination continues to fall, chances of these serious diseases becoming more common increases - people who don't get the vaccinations on grounds that they have never heard of any pet falling ill/ dying are relying on fact that vaccination has been widespread enough to prevent outbreaks.