HTTPS isn't only about encryption. It's about trust, search positions and ultimately about money.
User trust
Browsers mark sites without SSL as “Not secure”. A visitor sees the warning and closes the tab before reaching the order form.
SEO
Google officially uses HTTPS as a ranking signal. All else being equal, a secured site ranks higher.
Technology
Modern features (HTTP/2, Service Workers, geolocation) only work over HTTPS.
On WPHost a free auto-renewing SSL certificate is included in all plans — the switch takes one click.