Companies like twitter operate at a different scale. Lichess can off load hiring devs by using out of box solutions like paying for AWS, paying for cdn, using adsense to serve ads, utilizing thirdparty libraries, etc. For large companies, a lot of these are in house solutions, because at that scale, it could be cheaper, they wont as dependent on other companies for reliability, they have more control over where the data is being used or stored. etc.