Software Quality Assurance is a good practice that every large scale business should employ. IT related businesses have never hesitated to use SQA to ensure that the application they will release for their users or sell to their customers will live up to their expectations.
On the other hand, there are companies that has opted to forgo with the usage of SQA and relied on application testers just to make sure the application will never have internal errors. The SDLC on the other hand, will ensure the development of the application will work as planned.
Like other development plans, there are issues why developers and companies do not use SQA.