Since the early days of social media the concept of syndicating (or sometimes more commonly, crossposting) content from one service to another was a common pattern to increase the reach and discoverability of content online.
Most indieweb publishing flows include a step involving third party services.
Reasons this is important
- Proliferates your content/links to your content across the web
- Allows people who do not yet have an indieweb presence to catch up with your content
- POSSE: the preferred model, where content is stored under your domain before being pushed elsewhere
- PESOS: an alternative model, where content is posted to 3rd party services before being archived under your domain
- PESETAS: an even poorer model, where content is posted to 3rd party services, and aggregated/shared onto a single other silo (rather than your own domain).