That is clearly too late. It is also crucial to get QA input for project planning and scheduling. Finally, QA staff can do many things in parallel with design and implementation activities. This can save considerable time at the end of the project. A more insidious problem is created by schedule overruns.
Most projects work against a fixed deadline for delivery.
The deadline may be imposed by a customer, a trade show, or something similar. It typically is very difficult to move that end date, and in some cases, severe financial penalties or opportunity costs are associated with a slip. Related to the above phenomenon is the widely held view that the job is done once coding is complete. Some feel that testing is only there to catch problems introduced by incompetent programmers. And since most companies are proud of their programmers, the feeling is that testing is more of a luxury or safety net rather than the integral part of the software development process, which it is.