Sometimes that is true, but not always. If an invention is valuable enough to be stolen, there is a fair chance that it will be of interest to a second big league company as well, so you may find a partner with deep pockets. In the worst case, having a patent is a way to allow you to keep doing what you are doing with your invention. Having the patent yourself is a whole lot better than someone else having the patent on the same invention. Trade secrets are an alternative, if you are sure no one else will figure out how to do what you are doing for the economic life of the product.
Patents only last a limited time, after which the invention is available to anyone.
Another possibility is to publish the invention so that no one can ever get a patent on it. At least that way you will be able to keep on doing whatever you have been doing with the invention, even if others can also do so. Publication can be in any language any place, so long as it is publicly accessible. It could be on the web, or someplace very obscure. More than one has been down the same road.