If you don't trust anyone from your family, why would you trust a company?
You're not trusting a company, because you're not giving them your seeds. There are ways of doing that using encryption.
Just note down your seed and give it to your wife/father/brother/son.
Whoa, really?? Many wives have poisoned their husbands or killed them in countless other ways in order to get the payout on a life insurance policy. Probably at least a good number of those husbands thought they could trust their wives not to kill them for the loot, which turned out to be a very expensive self-deception. And consider that it doesn't have to go as far as murder for that sort of thing to go badly wrong. What if the wife takes the bitcoins and runs off with her yoga teacher? The poor doting husband will have plenty of time to think about his mistake as the two lovebirds enjoy a long Caribbean holiday at his expense. As for brothers, history is full of brothers killing brothers for wealth, power, and other motives. Similar examples could be cited about fathers and sons.
If you don't trust your heir, why would you care to inherent them anything at all
Some people care about family members even if they're complicated and not always the most reliable people. Or if, say, they have a drug or gambling habit. In such case, one may trust the heir to an extent, but not all the way. And not with their money. People have a way of thinking that any money in their possession, no matter how it got there, belongs to them and is theirs to do with as they please. You might think you know someone and end up being surprised.
Imagine an old father who has three daughters, one of them being an angel and the other two a pair of devious, drug-addicted schemers who have always been trouble. He may still want to split his fortune three ways between them. One of the bad ones could even be his favorite, for some unfathomable reason. So he cares about her, even if she doesn't deserve it. This is one example where it might make sense to hire an inheritance service. He might try leaving it all to the good daughter and trust her to honor his dying request to give the others their fair share. But even she might be tempted by a thick stack of crypto to make an exception to her principles. Encryption and due diligence can help keep the honest ones honest.
And theft isn't the only way that your intended heir can cause you to lose your crypto while still alive. If they're not tech savvy and don't understand the basics of cybersecurity, they might do something silly like save a plain-text copy of the seed phrase in their email or something like that, or even fall for a phishing scam. That way they deprive you of your wealth without even meaning to
Hey, anyone who wants to is free to just give their seed phrase to their heirs and trust them 100%. But if you do, make sure you don't forget any birthdays or you can kiss your crypto goodbye!