I have a good hosting account. However, many forums load your photos onto their servers rather than simply linking to the user's host.
The problems with most free photo hosting services are: 1, they eventually want to make money, so they suddenly begin charging a lot, and people drop them, leading to broken links in old forum posts. 2. They have limits on the space a free user has, so people delete images to make room for new ones leading to broken links in forum posts. 3, they change the URLs for images that the user reorganizes, leading to broken links in old forum posts. 4, they go belly-up, leading to broken links in old forum posts.
I warned people in a great gun forum about this for a long time, and when a certain free hosting site suddenly started charging an exorbitant rate, they all dropped it...leading to thousands or hundreds of thousands of broken links in years worth of old forum posts.
Anyhow, that broken link business is why a lot of forums choose to store and host all images rather than relying on the members' many, individual hosting services. It is really disappointing to be reading a thread and then have the images in a potentially helpful or interesting post all be little missing image icons instead.
I prefer to use a paid hosting service myself, because I not only want my old forum posts to retain the images I have posted, but I do use it for some professional work, as well.
But really, I was mostly joking with my post above.