When should you use "to" following a "why"?

Solution 1:

Both of these constructions can be considered to be elliptical forms:

Why To Treat Your Product Like It's Finished.

[The reason/s] why [you should choose] to treat your product like / [as if] it's finished.

(Note that the question mark would be non-standard for a non-direct question, as in this sentence fragment. Of course, you can justify the use of one by positing a missing [What are ...])

Why Treat Your Product Like It's Finished?

[What is the reason / are the reasons] why [you should] treat your product like it was / [as if it were] finished?

Elliptical forms often occur in a choice of flavours (and clarity).

Solution 2:

As far as I know, "why" can be followed by "infinitive without to". This structure suggests that an action is unnecessary. Example:

Why argue with him? He'll never change his mind (In this example, it's not correct to use "to infinitive" or "-ing form" after why).

Solution 3:

Why To Treat Your Product Like It's Finished?

This is not actually a question. Here why is not functioning as an adverb, but a noun. In this sense it means something like the reason(s).

e.g. Let me tell you why you should learn French = Let me tell you the reasons you should learn French

As an article title: Why To Treat Your Product Like It's Finished = Reasons To Treat Your Product Like It's Finished