Why should I bother building a brand or becoming famous on LinkedIn?

You don't really need to bother posting on linkedin unless there's clear value for your brand you're trying to build through social media. I personally post on linkedin every day trying to connect with Mr. Beast to only satirize how linkedin is mostly filled with low quality influencer content.

Having a giant megaphone always has value, and that's pretty much what building a known brand is. You might not have a use for it right now, but there's a lot of viable use-cases that could occur for you later on:

1. Getting job opportunities - The folks I saw bounce back from getting laid-off were often those with bigger LinkedIn followings. The "Please support me, I just got laid-off" posts already have a 5-10x organic multiplier on LinkedIn, so having 10,000 followers instead of 1,000 will help you capitalize on that moment even more. Also if you have a reputation on LinkedIn as someone who shares good engineering career advice, I'm sure you'll get more inbound naturally from recruiters as well.
2. Bootstrapping your own thing - Whether it's a side project or creating your own startup, having a "pre-made" audience is very valuable. For Taro, we even got investor reach outs through LinkedIn.
3. Plugging causes you care about - I also see a lot of people point their audience towards charitable organizations, movements, and communities they want to see grow.

What's in it for very senior engineers?

As a fairly senior engineer who posts to LinkedIn way too much and is mentoring several other engineers on doing the same, here are some additional reasons:

1. Altruism - The engineering audience on LinkedIn is overwhelmingly junior so tech career advice that's relatively basic for you and me like "You should attach a test plan to your diff" is genuinely insightful for many engineers on LinkedIn. LinkedIn is almost certainly the most efficient and scalable way to teach a ton of engineers on the internet.
2. Sharpens teaching skill - LinkedIn's character limit is fairly limited, and you don't want to come close to hitting it anyways as social media attention spans are short and longer posts are almost always severely punished. This means that you have to get good at conveying valuable information in a very concise way to succeed on LinkedIn. This teaching and communication skill is fundamentally valuable, and teaching in general is a good way to sharpen your own understanding of a topic.
3. Meet other great senior engineers - Over the past couple years, more and more senior engineers are realizing how powerful LinkedIn can be. However, it's still at a sweet spot where they aren't that many very senior engineering LinkedIn influencers who actually know what they're talking about. This means that if you get in now, you could build a pretty sweet network by joining this illustrious group. The senior density is far lower than Twitter, but it's improving for sure and unlike Twitter, LinkedIn isn't a raging dumpster fire.

If you're interested in building your presence on LinkedIn, I recommend joining my upcoming event: How I Get 500,000+ LinkedIn Post Views Per Week - By Alex Chiou

Take action to increase your luck surface area. One of the best ways to improve your odds of getting lucky is to become top-of-mind when it comes to a job, topic, or other domain.

Posting on LinkedIn consistently is one of the easiest ways for you to build that expertise.

For me, it led to valuable connections. Concretely, I was able to teach a LinkedIn Learning course back in 2021 due to the network I was able to create.

When people disagree with me, I learn from it.

I learn that I wasn't clear - and hopefully how to be clearer in future.

I learn how to better convince others when I am right.

And most of all I learn something useful when I'm wrong.

Alex hit on a lot of great points in his post. I'll add a few more from my POV.

If you're looking to advance your career: Treat your post history as your personal content library. It can be extremely powerful when job searching or making new connections. Relying purely on your LinkedIn profile and CV is difficult to properly showcase all your expertise. For example, you might only spend one line on a CV on an accomplishment, but the journey you took to attain that accomplishment is better expressed through a series of posts or newsletter articles.

If you're running a business (especially in career services): LinkedIn is one of the best ways to generate leads and nurture them over time. There are several mid to high 6-figure businesses where LinkedIn is their primary channel.