The social space is congested.
This isn't news - you have a maximum of 4 seconds for content to capture your audiences attention or they're scrolling on. It makes sense your followers also don't want to have to type or click to much to hunt down your content away from where they currently are.
Searching for page: Min 4 Clicks
Direct Link: 1 Click
And this doesn't count someone who doesn't have the website bookmarked or needs to switch apps on a phone and search. You can add easily 10x more clicks than from a direct link, and that's still including some shortcuts - all while not guaranteeing they even find your page at all (or don't get distracted on the way).
What's strange as well is that teams haven't always just thrown a post online. A lot of thought has gone into grabbing the audience's attention - but not necessarily on the next step, driving and guiding them to your desired destination.
I see this an awful lot on Gameday, and across most sports. Generally this lack of direct links doesn't really make sense either. If you had an article on your website you wanted to make your audiance aware of you wouldn't just put in the copy "head over to our website" - you'd add a link. It shouldn't be any different for informing someone of something happening on another social platform.
Social media & Google might make it easy to find your official page on other platforms - but why create the extra effort when you can take all and any effort out and add the direct link? It's not like it looks messy either.
In the constant fight for attention and relevance, those who streamline the process and make the experience easy for their audiance will come out on top.
Don't add extra work - make it easy.
Keep It Simple (on Social) Stupid.