Because ABN AMRO is required by law to pass these details on to the Dutch tax authorities. In 2016, there was a change to the legislation:
Common Reporting Standard (CRS), this is international legislation
Foreign Account Tax Compliance Act (FATCA), this is US legislation
If you are liable to pay tax outside the Netherlands and you have earned money from the sale of investments, these proceeds are shown. The Dutch tax authorities will ultimately forward these details to the tax authorities in the country where you are liable to pay taxes. ABN AMRO only shows details on the Annual Statement that are relevant for tax purposes.