Все по большому счету из за налоговых ставок. К примеру в Чехии дела обстоят так: "Czech Republic has a corporate tax rate of 19%. Companies that operate under VAT have to pay tax on purchases at 21%. Certain services, like those related to foodstuffs (excluding essential child nutrition), some of the soft drinks, take away food, water supplies, medical equipment for disabled persons, children's car seats, and others, benefit from a 15% VAT rate."
А в Бельгии примерно так: "Belgium has a corporate tax rate of 33.99%. Companies that operate under VAT have to pay tax on purchases at 21%. Certain services, like those related to food, water, pharmaceuticals, domestic transport, printed books, periodicals, and others, benefit from a 12% VAT rate."
Источники: http://www.confiduss.com/en/jurisdictions/czech-republic/business/company-formation/ ; http://www.confiduss.com/en/jurisdictions/belgium/
Казалось бы, разница относительна невелика, но каждый процент это миллиарды евро.