These monopolies would cause serious problems for users and developers of computer software and systems. Imitating interfaces, sometimes with changes, was standard practice in the computer field. Most computer companies, and nearly all computer users, were happy with this state of affairs. Imagine if each car manufacturer had to arrange the pedals in a different order. Software will become and remain more expensive.
Large companies have an unfair advantage wherever lawsuits become commonplace.
Since they can easily afford to sue, they can intimidate small companies with threats even when they don't really have a case. User interface improvements will come slower, since incremental evolution through creative imitation will no longer be permitted. Even Apple, etc., will find it harder to make improvements if they can no longer adapt the good ideas that others introduce, for fear of weakening their own legal positions. Some users suggest that this stagnation may already have started. If you use GNU software, you might find it of some concern that user interface copyright will make it hard for the Free Software Foundation to develop programs compatible with the interfaces that you already know.