Open Street Maps. It has some gaps or missed addresses/neighborhoods/roads because it is built on contributions of volunteers.

For self-hosted hobby instances, expenses are likely all out of pocket. Instances amassing a large amount of users could potentially be driven to aggressive financially-driven changes of how their instance works, to maximize exposure to ad posts or sponsored pinned posts, for example. Donation-centric contribution helps alleviate that kind of seeping financial platform degradation.

Not until the tendency for the mainstream to gravitate to centralization is changed. Lemmy will need exponential growth to become large enough in userbase to be a mainstream consideration to use the federated replacement.

lemurs > lemmings