Because people won't trust google soon (google != alphabet). When adblockers are fully implemented and used by the entire population, google will look like societ russia after the collapse of the CCCP. It is going to start moving into any business where information is valuable (every business) and it will be super scary as they have the entire worlds data and they have been using it to train a very complex and highly sophisticated AI for nearly 2 decades with billions of records of training data a second in every category you can imagine.

So people will want to protect their data & privacy, especially companies.

People will want to have a better search experience, which means that things that are on the internet that they want to see will be there. Google is probably the most monitored for takedown requests/deindexing and they control most of the video portals and certainly the window you view the interent through so they are a target to legitimate and illegitimate takedown requests.

edit: they also have built the components and outsourced them. Hadoop/Map Reduce, most of Apache's products, elasticsearch, and another google offering tensorflow can certainly be made into a search engine. Obviously not google scale, but certainly an individual.