The vessel also serves a purpose for the spirit connected to it. The vessel can be charged up to give the spirit more energy and (magical) power. This is why it is important to keep a vessel charged. This can be done in multiple ways depending on what type of spirit is attached to the vessel.
Having a spirit "bound" to a vessel does not mean you have complete control over said spirit. The spirit is not a slave to you. I know this is a concern for a lot of people which is why I bring it up.
Some spirit can be forcefully bound to a vessel, yes. Djinn are a good example of this as there are a lot of stories about djinn being bound to an item against their desire. Sometimes it is necessary in the story if the djinn is trying to destroy everyone. Usually though, djinn and other spirits choose to be bound to a vessel. Like I mentioned earlier, spirits also get benefits from being bound to a vessel. For example, they can easy get energy through the object and have a more direct line of communication to the person holding the vessel.
I have found that most sellers are not forcing conjures and binds. The people that try to scam buyers usually don't even bother trying to conjure up spirits. Instead, they just sell jewelry or crystals that they claim have a spirit attached to them. They are usually not involved in the spirit keeping community either. But this is a topic for another post later.
A vessel is an agreement with a spirit. Why would a spirit agree to such a thing? Some spirits just want to. They live way longer than us too so our lifetime to them is actually very short. Spending a human's life with a person they like is not that time consuming. It also gives spirits from different realms a chance to interact not only with humans but other spirits as well since most spirit keepers have a variety of spirits working with them. Spirits are interested in us for the same reason we are interested in them.
Some spirits will want to work with you but will refuse to be bound to an item. Do not be offended by this or feel like the spirit hates you. Some spirits just do not like the idea of being bound to an item. Sometimes it takes time. You can still have a close relationship with these spirits. Usually these types of spirits will be local nature spirits that are already attached to nature through something like a tree or lake. These local nature spirits are bound to these areas and will not want to leave.
