They can also be fairly insulting in tone. I guess us oldsters are too "thin-skinned" for today's hyper-competitive world. We make unreasonable demands, like being treated as humans. We're supposed to ignore mortal insults. Maybe it's just like a hazing ritual, where we are supposed to prove we are willing to abase ourselves for the corporation.
Work environments are also completely centered around the needs and desires of younger folks. In many cases, it's not deliberate, but these are companies that are run by people in their twenties, and staffed by people in their twenties, so the sample population is a bit...homogenous. Perks are designed to entice younger folks (like hiking and skiing offsites, no weekends, Friday night happy hours and pub crawls, free beer and food, open-plan, "hip" offices, Urban locations, T-shirts, no short-term disability, etc.).
The recruiters are just plain rude. They ghost me, almost immediately after finding out that I'm older than 35 (a lot older). Very different, from when I used to look, before my last job.
The LeetCode tests are "Young-Pass Filters." They generally cover topics that people fresh out of college would nail, and I know that many engineers spend countless hours, practicing LeetCode (maybe while they are supposed to be writing non-leet code for their employers). How do I know it? Because I keep getting notifications, when they post their results on LinkedIn and other places.
I've learned that if I see a binary tree test, I might as well look elsewhere.
I have been writing shipping code, since 1987. I seldom encounter the neat little problems that I see in whiteboard tests. Just yesterday, I was dealing with some weird threading/memory leak issues; and those are a blue-assed bitch to debug (spoiler: I fixed them). Every single day, I have big, nasty problems that need to be fixed, and every single day, I fix them; often by designing good, robust, high-quality frameworks, modules, and applications. Device I/O problems are fun, too.
The most unfathomable thing, is people directly and unapologetically, ignoring my portfolio. I have a big one. Real big. I know that it isn't that special, because I see bigger and more impressive ones, all the time. There's a lot of really talented, experienced developers, with years of work, open to perusal.
These folks are looking to hire critical-path talent, responsible for the lifeblood of their products, pay us six figures, and then they deliberately ignore resources that could tell them more about us than twenty hours of interviews. People could make the "hire or ignore" decisions, simply by reviewing the portfolio. They wouldn't even need to call me on the phone, or let me know they were interested, in any other way. Complete stealth.
But, like I said, I'm not particularly interested in rejoining the "rat race." This forced me into an early retirement, and I'm fine with that. I work harder, these days, that I ever did, and it's a joy.