Growing Virally (where virality coefficient and cycle are really important[1]) is different than growing with Paying Users (where Lifetime Value (LTV) and Cost to aqcuire customers (CAC) is really important[2]) that its different than growing through very high retention rates[3]. You can achieve P/M fit with any of them.
You can argue that you don't need growth. Which investors won't particularly like (in particular, VCs have LPs to give a return on investment[4]). But ultimately, if your company is not growing in any way, is any of your work actually making a difference? Are the people working on the company getting a return on investment on their time investment?
Growth also doesn't need to be about money (or eventual money, as it can be the case if you are growing virally). Think of Khan Academy (which is a Non Profit[5]): they can grow on more people using them, and on people using them more. They can also grow on impact they have on the students.
You can argue that you don't need growth. Which investors won't particularly like (in particular, VCs have LPs to give a return on investment[4]). But ultimately, if your company is not growing in any way, is any of your work actually making a difference? Are the people working on the company getting a return on investment on their time investment?
Growth also doesn't need to be about money (or eventual money, as it can be the case if you are growing virally). Think of Khan Academy (which is a Non Profit[5]): they can grow on more people using them, and on people using them more. They can also grow on impact they have on the students.
[1] http://www.forentrepreneurs.com/lessons-learnt-viral-marketi...
[2] http://www.forentrepreneurs.com/startup-killer/
[3] http://larslofgren.com/marketingbasics/the-three-engines-of-...
[4] http://www.danshapiro.com/blog/2010/08/vc-insanity-economics...
[5] http://en.wikipedia.org/wiki/Khan_Academy