Bonuses are not created equal amongst the players around the world. Some regions get better welcome offers, better campaigns and all around more bang for the buck. The rule of thumb here is that more the people in that region play, the better the offers are.
The idea behind all bonus offers is to attract new customers and who better to attract than those who play the most. These players are the most wanted customers and every casino wants them in their team. This creates an arms race, where every casino is one upping the next and claiming the title of the best casino bonus.
The question then remains, who is the most wanted player, and the answer is a Finn. Finnish people gamble the most in the whole of Europe, which makes them the best customers for casinos operating inside the EU. This means that the casino bonuses in Finland are better than the offers for players in Central Europe or other parts
Thanks to a common currency, the euro, and these differences are easy to spot. You can clearly see the groups of countries that get similar bonus offers and those who get more than others. This is not limited to just match bonuses. Free spins, referral bonuses and other special offers differ depending on where the player is located.
Although Finns play the most, Finland doesn't sit alone on the throne. All of the Nordic countries get the same high bonuses, as all of these countries play a lot. If a casino can be popular among the Nordic players, it will start to make a decent profit.
The downside to this is that there is not much you can do about it. The only way to systematically get better bonuses is to move to Finland and play from there. One the other hand, this is a good indicator for players outside the Nordic countries. Look for those casinos that attract Finnish players and you will find a high quality casino that offers a lot of good bonuses and campaigns, even if you might not always get them as big as the Finns do.