Why are you so sure of this? Government granted monopoly is not the only incentive to create something, but there are definitely countless examples of how patents have been used to squash innovation and disruption.
I grant that patents have had some positive effects, but I would not assume they are net-positive. Also, they were primarily designed in a time when there were fewer ideas and getting things into production was much more expensive (this applies to physical things, let along software with zero marginal cost), and it was much easier for an incumbent to steal an idea and crush a startup simply by the barriers to entry to manufacturing and distribution. Since then lobbying efforts have only pushed intellectual property rights in one direction. Even medical research patents which are often held up as necessary create perverse incentives that tie up R&D dollars in unproven new drugs, and making arbitrary tweaks to existing newish medicines in order to secure patent protection, making research into natural or public domain compounds come to a standstill regardless of efficacy.
Obviously I'm biased since I work in software, but I think we'd be fine without patents. Trademark and copyright address much more important issues in my opinion.