These are typical errors made by the native speakers. Most (every?) language has rules, which are more difficult for a native speaker to follow vs. a well-spoken foreigner.
Other examples in English are:
- who vs whom
- then vs than
- ask vs acks
Less vs fewer.
Very few people say "acks" instead of "ask". It's not a common error at all. I would say "who"/"whom" is the only truly common one you listed, though screwing up "than"/"then" is at least common enough that one runs into it with some regularity.
Ask vs acks is just a regional pronunciation variant, nothing inherently wrong with it. I have noticed that a lot of people from backgrounds with enforced language uniformity (french and Russian speakers for example) have trouble with the idea though.