How else do you expect to get a users profile picture? Chat messages don’t contain the link to profile pictures because Twitch Chat has no use for profile pictures.
If you want to get a users profile picture you should use the Get Users endpoint https://dev.twitch.tv/docs/api/reference#get-users and buffer requests so that you’re not making 1 request for each user entering the chat command but instead it waits a few seconds and then make a request for up to 100 users at a time.