It's incredibly difficult at that time to counter raiding víkingar due to the delay in communications between their target and any large body of standing troops - usually the local leader's posse commitatus of household troops - so by the time they did arrive, there'd be no more víkingar to fight.

If you're asking why the English didn't launch counter-raids against the Danes or the Norwegian petty-kings, well, launching an amphibious invasion against another country requires an exceptionally strong navy, which is something that, during the most active time for raids by víkingar, the English didn't have.

Additionally, in the vast majority of cases, there was no state (or quasi-state) backing for raids by víkingar. Individual warlords (commonly referred to as Sea-Kings in the sagas) would get groups of like-minded brigands together and attack, plunder, then bugger off as quickly as they could so that they could all enjoy the loot and slaves.

It is incorrect to assume that the English did not counter Viking attacks. Details and outcomes of warfare between English and Norse forces were recorded. Indeed, in the earlier instances, populations were taken by surprise and unable to mount effective resistance, but this changed during the ninth century. In particular, during the reign of Alfred, the English were able to develop an effective navy and consolidate their forces to repel the Danish incursions. The period of Viking activity throughout Europe was hardly the one-sided event of slaughter that popular opinion imagines. Some primary sources for this period include The Anglo Saxon Chronicle and Asser's Life of King Alfred.