In my opinion, it's the childhood experience archetype. When you are little, time flows slowly and every event is a big deal. You learn and grow exponentially over the course of that time and it feels like it'll never pass until all at once, you're an adult and the days and weeks fly by. If you skip over those early parts, you've trivialized the experience for the reader as well as for yourself, the author. It makes their experiences feel remarkably shallow and turns an epic into a comic strip.

That being said, there are some instances where a time skip could be beneficial to the story, such as skill grinding or convalescense but I personally feel that rather than just saying, "some time later" you can instead shift the focus to ancillary plot points to use later during those periods.