At much more than 10k posts, the display time for simple pages gets longer, searches because slower, and so on. In part, it is because of the query that selects the posts for display, it has always had a pretty major flaw in it's layout, the query is done in a way that makes the indexes pretty useless. I have added indexes to all the blogs I run just to be able to keep up with day to day, especially on the larger ones.
Adding significant numbers of extra records is never a good idea. Just correcting a typo is a new records. Notice 2 or 3 on seperate shots and suddenly you have 4 times the data for the same post.
Wiki is different from a blog, in that most of us are the only ones editing our own blog, or at most 2 or three people. Wiki had to add in an edit history mostly to deal with people defacing entries. Wikis are a very, very different game, and they use a significantly different methodology in order to avoid DB issues. It's like a car, putting a ferrari body on a yugo still leaves you with a yugo.
In the case of wordpress, it would have been better to add a table called wp_revisions, where the old post is written off to each time the edit screen is accessed. The only time you need to look at revisions is during admin time, your blog readers aren't checking your revisions and certainly you aren't showing them to the search engines. Those combine for 99.9% of all wp_post queries, so why do it any other way?
The reasons for disabling it? Because the vast majority of the people writing personal blogs don't need it. Most write a post and that's that, and they might fix a typo. They don't have 10 people coming in writing stuff, they aren't worried about anyone defacing a post, etc. I am sure that some people may use it to recover a post when they do something like accidentally remove a post, but for the most part it is going to be tons of data that most people will never use, and that will go stale almost immediately.
Modern UI design says "give the users the options", not "lock them into a single way of thinking". Using that logic, there would be no need for plugins or themes because we would just all use the one right theme that someone has selected for us.