Uber I can still believe due to their complex app (real-time tracking of drivers and riders, matching algorithms, route mapping, pooling, fare calculation, surges). Not to mention other divisions like food delivery, autonomous driving, freight etc.
AirBnb is...a database of static listings and a search engine on top. Their top technology problems were all solved by Expedia like 20 years ago.
Uber is not that difficult. There's work for hundreds of developers between the few products, the localization for tens of countries with different language/currency/culture, and maintaining the main applications in working condition 24/7 at global scale. That's about it.
They have thousands of engineers sitting idle or making pet projects, struggling to justify their existence, as regularly attested by internal employees when an article pops up.
AirBnb is...a database of static listings and a search engine on top. Their top technology problems were all solved by Expedia like 20 years ago.