Code signing guarantees that an app you're installing is from a reputable developer. This means it is trustworthy and is safe to open. It's the digital version of a seal on food to ensure no one has tampered with it since leaving the factory.
Code signing is an important part of distributing an app to users. Without it your users will get warned that your app may not be safe and they should treat it with caution. At worst they may not be able to run it at all.
The yearly cost of code signing certificates alone is $200 more than ToDesktop
Code signing is not a trivial process. It requires significant investment in time and money to do right.