Question: I paid for an SSL certificate from Namecheap, I think it was certified by ComodoSSL. It cost me 7$, it took them a week to activate and I had to do it myself from SSH while editing my site's configuration files.

Then a friend made me aware of [Let's Encrypt](https://letsencrypt.org/) who not only give out free SSL certificates, but they can be installed by running a single command.

I'm sure I'm missing something here, but why would I want to pay for an SSL certificate when I can get one installed easily, for free, with automatic renewal set up?

Answer: 
LetsEncrypt certificates are great. I use them myself instead of buying certificates. There are a few drawbacks:

* LetsEncrypt certificates only last 3 months. Most purchased certificates are good for one or two years. That means that you absolutely need an automated process in place to renew your certificates or it is going to be too easy to forget.
* LetsEncrypt only offer the lowest validation type of certificate. Domain Validation (DV) only validates that the owner of the certificate has control over the domain. Organization Validation (OV) certificates also check the documentation of the person or company requesting the certificate. Extended Validation (EV) certificates require even further checks. The better your certificate, the harder it is to be forged, and the more your site's authenticity can be trusted because of it. In practice, browsers only give a visual nod to EV certs, usually showing something in green in the address bar for them. Up to this point, most users don't know or care about the different validation levels.
* Wild card certificates are a bit harder to obtain from LetsEncrypt. From other places you generally just pay more money. LetsEncrypt requires DNS validation for wildcard certificates.

Historically, security certificates have always cost something. Other companies that have offered free certificates have come and gone. I used to use StartSSL which offered a single domain free certificate until they did some shady stuff and browsers stopped trusting their certificates. LetsEncrypt has fewer limits than previous free certificate vendors and is far more automated. It also has some big supporters such as the EFF, Mozilla, Chrome, and Cisco. See <https://letsencrypt.org/sponsors/> It appears to be well enough run that I expect it to be around for years.
The simple answer to this is many webmasters just don't want to do these things which unnecessarily consume their precious time. In case of letsencrypt its easy to use and free but you have to remember and re-install the certificate every 3 months. If you don't or just forget to do it then you site will show 404 error to your visitors and search engines.