Patents allow algorithms to be protected. Software trade secrets do not promote dissemination of valuable algorithms. Software patents provide motivation to investors in software companies, since their investment can be returned through licensing arrangements for the patents so produced.
Patents work well in other industries, like the mechanical components industry or the drug industry.
Copyrights work well in the music and book publishing industry. Cross-licensing of patents by corporations will occur. Advocacy of the abolishment of software patents is extremism. Reinvention in software does not occur often. Software patents define a legal monopoly which is morally unsound in a free market.