@ad951bfd Part of the explanation is probably that the Vikings were moving coinage from areas with a really well developed market economy to their home where there was little that money could buy and definitely no rulers who could decree older coin types invalid. Both factors favoured hoarding. You could buy a farm or pay a bride price with kilos of silver, but there were no shops where you could spend small sums. 

 @34cb1247 well that makes sense!