Because the Bank Holiday situation is not consistent throughout the United Kingdom – we all live under the same government so therefore we should receive the same number of Bank Holidays.
In Northern Ireland they receive 2 extra Bank Holidays (St Patricks Day and July 12th). In Scotland many places still have local Bank Holidays (Glasgow Fortnight / Ayr Gold Cup etc).
This means that those of us in England & Wales receive fewer Bank Holidays than the rest of the UK which is unfair given that we all live under the same government. The number of days received should be brought into line so that we all receive the same. It is worth noting that many Civil Servants get extra days too (3 days at Easter, 2 days for late spring Bank Holiday). These should either be scrapped or given to everyone else.