A starliner is not nearly as reliable as a Boeing 777. Just look at what happened to the space shuttle. That’s also why Russians had reliable launch vehicles but not so reliable jetliners.
If airplanes had the same failure rates as even the most reliable rockets in existence, we'd be seeing tens to hundreds of crashes per day. Of course it's not because rockets are "allowed" to fail more regularly, but because this is the best we can currently manage.