This is the smart approach. Keep everything as "format agnostic" as possible. The only reason someone would not use this approach and opt for one of the servi

This is the smart approach. Keep everything as "format agnostic" as possible. The only reason someone would not use this approach and opt for one of the services mentioned is marketing. There is no marketing for storing files in a "non-proprietary" format. It's simply a matter of not knowing how to do it. What's funny is the proprietary approaches ultimately can make things more difficult for novices. At least it's more they have to learn: different rules for each service. How often I have heard novices wanting to know how to convert/export/transfer files to/from these services. Compare this with learning the jpeg format, IPTC and EXIF. You only need to learn one set of rules. And every service uses jpeg. That's unlikely to change anytime soon. It's a battle against the "lowest common denominator" in the interest of creating a strategic advantage via incompatibility and proprietary formats. But it seems always some compromise is necessary. All those services work with lowest common denominator formats like jpeg. They don't each have their own proprietary image formats, though they could. Compromise is made. The entire web is built on "lowest common denominators": e.g., IP, UDP, TCP. To allow things to flourish you have to have some lowest common denominators that everyone can develop on top of. But let the battle continue. We the users all suffer inconvenience as a result.