Because software quality begins at the source.

In 24/7 productive environments the common saying "time is money" is mandra like recapitulated almost like in a prayer wheel. In normal end user environments it's not as hard as in production, but a software tool which needs a minute to update a spreadsheet or a presentation to show, is not liked very much by its users. Therefore, execution speed is an important point in software development. But, speed is always less important than data safety and stability.