* As the web gets faster and gains more capabilities, it will encompass everything apps currently consider their domain.
* By default it contains no gatekeepers, whereas apps on mobile devices primarily go through one central source. This carries with it safety, but also a higher barrier to entry: And generally, higher barrier to entry is something people are only willing to endure if given good reason to. Having the web replaced by apps doesn't leave any room for that.
* The web is open and universal. This gives it infinitely more resilience than apps- if Apple were to fall into the sea, an entire ecosystem would be lost. As is, the web practically guarantees nothing can ever die permanently.
About the only weak point that the web has, is that it's more difficult to effectively monetize one-time payments, but that's why everyone and their sister is going to subscription models, or are working within an established marketplace.