Why choose servers in Belgium?
Your server's location affects three concrete things, and two of them matter to almost every Belgian organisation.
Speed
The distance to your visitor determines latency. For a Belgian audience a Belgian server is measurably faster than one across the Atlantic. Not decisive for a simple site, but very much so for a shop or an application.
Data legislation
Data within the EU falls under one clear framework. Outside it you need additional safeguards that you must be able to explain to a customer or a regulator.
Support
Time zone and language. A problem at nine in the morning here is a middle-of-the-night problem elsewhere. That difference shows in how long it takes to resolve.
What matters less
Location is not a direct search ranking factor, despite what you still read. Speed is, and that is how location works indirectly.
Worth checking
Ask where the servers actually stand and where the backups go. Those two answers are not always the same.