Self-hosting gives you freedom. You own your data. You decide what to do with it. You are not under constant risk of getting your account banned because of a false-positive. You are not censored. You are not held hostage by any service provider. Self-hosting is the only way we can retain control over our data. Host your own website using Ghost or Hugo. Host your own text/audio/video chat server using Matrix. Host your own cloud storage using Nextcloud, your own search engine using Searxng, your own adblocker using Pi-hole and WireGuard, and your own code using Gitolite.
One of the main reasons why self-hosting is so important now more than ever is the behaviour of big tech companies. They have lost all credibility and they should not be trusted with any more of our data. There have been too many scandals over data misuse involving big tech companies such as the biggest search engine plus email provider, the biggest social network, the biggest e-commerce company and the biggest operating system by market share. I don't want to single them out. Those are just the prominent companies which should behave responsibly. But they don't. And the whole 'making the world a better place' and 'we want to connect the world' announcements are just empty marketing slogans.
The only thing big tech companies want people to do is to use their products and use them all the time. Upload, watch, share, comment, like, post, email and chat. Do anything and everything. But do it within their walled garden. Give away data about yourself, piece by piece, but a piece none the less. The more data you give, the better for them. They can then analyse who you are, what you like, what you dislike, what gets you outraged and what makes you docile.
Big tech companies will then package this information in a profile and build it over months and years as you mindlessly use their platforms. But hey, it's free to use so what's the problem, they ask. The problem is, you're not the customer, you're the product. The advertisers, on the other hand, are the customers. You are the audience that tech companies deliver to the advertisers. Advertisers get to target their ads based on the profile tech companies have built on you.
And don't forget state actors too. If a company has a trove of data about its customers, sooner or later the government or law enforcement agencies or intelligence agencies are going to come in and demand access to it. If a company wants to operate in a country, it's obvious that it has to follow law of that country. The law often includes provisions of handing over user data for vague criminal offences like 'disturbing peace and harmony' or 'posting anti-national content' or siding with whatever boogeyman the current goverment is telling its followers to hate. It may not be you today but it can be you tomorrow when the government changes. But we provide data only after the state actor provides a court order so it's all legal, they say. But they forget to tell you rubberstamp courts do exist in democratic societies.
May be you're living in a dictatorship and your internet access, like your freedom, is severly restricted. You will be in an especially risky situation if you have to carry out confidential conversations using a product of a commercial make-shareholders-happy-at-any-cost company which will gladly hand over user data, or even worse, add backdoors, rather than risk getting kicked out of the country.
Sorry for ranting but this is why I believe that in today's world it's better to self host as many services as you can rather than relying on big tech companies and hoping they would do a good job. Own your data and protect your privacy by self-hosting.