The other day I had a discussion about the Dutch verb willen 'to want'. It is a funny verb, because it formally has two past tenses. Both wou and wilde.
I was watching a movie in which the form wou was used in the subtitles and the person who I was watching it with pointed out that it looked silly and was incorrect. She claimed that wilde was the correct formal form. Luckily our lovely language hasn't been prescriptivised to a level that a perfectly correct form like wou is deemed incorrect, but it does show how people feel about it. Even I tend to avoid wou when writing formal letters.
The funniest thing is, wou is the historically correct form. willen belongs to a small class of funny germanic verbs that are ja-verbs in the present, but behave as normal verbs in the preterite. So, willen goes back to *wiljan while its past tense is a perfectly normal Germanic preterite *wal. In other words, it's a strong verb.
In general though ja-presents are weak verbs, while those without a suffix are strong, and this is the reason why it was changed to wilde. For example rillen 'to shake' has a past tense rilde from *riljan and *riliða where in the preterite the *j-suffix shows up in its vocalised form *i. By analogy of this class of verbs, a secondary preterite of willen was easily made, making the verb regular rather than irregular.
What I find remarkable is that, generally more 'formal' language tends to be a bit more archaic, but in this case, people seem to prefer an analogically levelled form over a form that preceeds it by well over a 1000 years.