Those companies are a product of the last wave, when Rails was very popular in tech, especially amongst San Francisco circles. There are also a lot of examples

Those companies are a product of the last wave, when Rails was very popular in tech, especially amongst San Francisco circles. There are also a lot of examples of that size that left Rails or never jumped on that trend. This is also an argument from survivor bias. You have to count the failures too, which we don't have numbers for. It's not that it can't scale; it's just that it's too easy to make a mess in the way, which would prevent you from doing so. So what ends up happening is that you pay for mistakes or someone else's, but at the end of the day, you are still on your own.