Samsung manages removable batteries quite well.
Also, while most batteries can last for more than two years, they gradually decrease in capacity. Interestingly, people often blame software updates for the resulting decrease in battery life. By providing user replaceable batteries, it is possible to get back to full capacity and use the old battery as a spare. I did this for my last two phones.
As for Li-ion batteries that actually wore out and got replaced, it happened on 3 devices : an MP3 player, a laptop and a phone.
As for the safety argument, I don't buy it. Battery explosions are extremely rare and happen on genuine models as well.
I agree with you that most people don't bother with tearing down and fixing anything. But some others do, even if it is just for fun, and for these people, iFixit is great. Don't call something useless just because it is only useful for a limited audience.