The announcement was made in an email to users, explaining that the change was being made to "provide the best experience to our customers."
Changes in Safari 12 designed to get developers to offer browser extensions through Mac App Store apps instead of the soon-to-be-defunct Safari Extension Gallery were also cited as an influencing factor.
As noted by The Verge, other apps like 1Password were updated to implement the new system within their native apps, but LastPass has decided to remove support for its native app entirely.
The replacement web-based app supporting the new extension system has been built with technologies developed in the company's LastPass mobile apps, which should make it easier to maintain the apps across the different platforms.
According to The Verge, the negative outcome of the switch is that the new app lacks some of the functionality of the native Mac app, like system-wide hotkeys. However, LastPass told MacRumors that users can expect the same experience, with access to features such as the Sharing Center, Security Challenge, Emergency Access, Account Settings, additional Hot Keys, and more.