Tax havens exist so that rich people, corporations, corrupt ruling cliques and criminals can avoid paying tax or launder/hide money.
Tax is of course what makes human societies work – the rich gain disproportionate benefit, so should pay the appropriate level of tax.
Governments fail to address tax havens in varying degrees because of the influence of those beneficiaries. They invent reasons to avoid solving the problem.
It is possible to close down tax havens and achieve the necessary transparency. See eg Richard Murphy’s excellent post re one of the biggest, controlled by the UK.
All it needs is the political will to do it.