Explain why it is important that software products are developed and delivered quickly. Why is it sometimes sensible to deliver an unfinished product then provide issue new versions of that product after delivery?

The reason why software products are developed and delivered quickly is because  

most of the time client cannot wait an extended time for the merchandise to be developed and delivered because the delay in delivery of software products might cause a loss for the client if that specific software is being developed for the client's business solution.   In some mission-critical applications like defense systems, space research systems in such cases software must be delivered as quickly as possible because the project which is getting into such area cannot await an extended time for a software package to be delivered as here time constraint is involved and delay in at some point might cause a loss for an entire ongoing project.

Explanation:

Sometimes sensible to deliver an unfinished product then issue new versions of that product after delivery because

Sometimes the software that has got to be developed could be very big which isn't possible to develop during a shorter time and even client cannot wait an extended time for he's software in such case only the primary main core functionality of the software is being developed and delivered to the client and in later version remaining functionality's are included and delivered. Even it is often the case that software that has got to be developed is very complex and should get lots of obstacles during development in such cases also only the core functionalities are being developed and delivered and in later version remaining functionality's are included.

3) Presence of bugs in software may also lead to issue a new version of that software after delivery and then fix the bug and deliver the new version to the client.