There is another factor going on here, which is that younger people often feel the need to "impress" the audience (both those in and outside their area) with how difficult their result is. For better or for worse, this is to some extent essential for grad students hoping to get faculty jobs, and assistant profs looking ahead to their tenure letters.
Once someone gets tenure, they can decide (depending on their personality) whether to keep up this ruse, or whether to aim to present results as simply as possible.
I agree that there is a general tendency amongst researchers at an early stage of their career to show off the hardness of their results, both in in their talks and in their papers. (I, for one, would write all of my early papers differently now.) However, I am not at all convinced that this is essential to foster one's early career, as claimed by the commentator.
When it comes to talks, as in other job-related things, I tend to be a follower of Paul Halmos. (See this compilation of his thoughts that recently appeared in the Notices of the AMS.)
....the purpose of a public lecture is to inform, but to do so in a manner that makes it possible for the audience to absorb the information. An attractive presentation with no content is worthless, to be sure, but a lump of indigestible information is worth no more.…
Less is more, said the great architect Mies van der Rohe, and if all lecturers remember that adage, all audiences would be both wiser and happier.
Have you ever disliked a lecture because it was too elementary? I am sure that there are people who would answer yes to that question, but not many. Every time I have asked the question, the person who answered said no, and then looked a little surprised at hearing the answer. A public lecture should be simple and elementary; it should not be complicated and technical.
I like to think that this is the message we should pass on to young researchers from the very beginning of their research careers. Building a reputation as a clear speaker, who can make difficult ideas and results accessible to her/his audience, can only help in one's career.
Isn't it going to be a huge bonus to be remembered as a person who gave a highly accessible and entertaining talk at FOCS/ICALP/LICS/SODA/STOC 2nnn? Why don't we tell our young colleagues that a talk at a generalist conference is essentially a public lecture? The result would be better talks at conferences, a happier audience, and an increased reputation for the speakers.