Various researchers have found that, with a few exceptions, innovators do not think that patents are very useful either for excluding imitators or for capturing

Various researchers have found that, with a few exceptions, innovators do not think that patents are very useful either for excluding imitators or for capturing royalties in most industries By this, do they mean that imitators are typically able to operate despite patent protection or that there aren't attempts to imitate? The latter does not really support the concluusion that patents are not useful/effective, since a lack of imitators is something we should expect if they were (though it also is not proof that they are). The former suggests some problem with the legal situation surrounding patents, since it is exactly what patent law is meant to prevent.