Firstly, if Google did offer this feature, it would likely be targeted by Search Engine Optimization (SEO) exploits. In essence, any time a new search parameter is introduced, there's a risk of it being manipulated to prioritize certain content—especially by those interested in gaming the system for increased visibility or monetary gain. If YouTube's search feature were to be plagued by such spamming, it could severely degrade the user experience and lead to Google having to strip it away. While not a guarantee, it's a probable outcome given the history of SEO misuse.
Secondly, YouTube's primary focus is on its recommendation algorithm rather than search functionality. With billions of videos hosted, the key goal is to keep users engaged by serving up content they're likely to enjoy, thereby increasing view times and ad revenue. The search feature, while useful, is not as integral to this objective. Further, offering full-text search could provide yet another avenue to manipulate the algorithm, which YouTube surely wants to avoid.
Finally, implementing and maintaining such a feature would require substantial resources. It would necessitate hiring teams of high-salaried employees to moderate and ensure fair use of the feature, adding considerable operational costs. Considering these factors, it seems that Google has made a strategic decision to avoid this feature for now.
That said, the fact that third-party solutions are emerging, such as the one shared here, shows that there's a demand for full-text search capabilities. It also underscores the potential that these solutions have when unencumbered by the constraints faced by a tech giant like Google. This provides a fascinating insight into the dynamic relationship between third-party developers and tech corporations and the way they can complement each other.