Cryptocurrencies with a stated maximum supply... ?

I have been doing some cryptocurrency research lately, focussing on those with a maximum supply listed on coinmarketcap.com. I wrote some code in Excel to pull data down from this site for easier analysis (Thanks for the API), and I find that less than 277 of the 1454 currencies listed actually show a maximum supply value. Out of the top 30 by market cap, only 12 have a max supply.

I happen to think that having a maximum supply is important for the long-term viability of any currency, so I am surprised to see so many of the top cryptos, plus many "recommended for 2018" ones, not having a maximum supply...

The main purpose of this post is to ask the question, "How important is it for a cryptocurrency to have a maximum supply?"