How long should I wait for graduate admission decisions before moving on? I really searched for advice on this issue but without any luck. So here goes.
Background: This concerns PhD admissions to Computer Science in the US. In the current cycle, I applied to ten programs with application deadlines ranging from early December to mid-January. As of today (March 5th '21) I have only heard from three schools and with two accepts and one reject. The schools that accepted me are in the middle and lower end of my preference, and the program that my application was rejected from is at the higher end.
The issue: That leaves seven schools I haven't heard back from (not even waitlist). People have told me that &quot;it isn't over till it's over&quot;, but it seems far too late in the cycle for these schools to still be evaluating my application. While I want to be hopeful, I also have to send confirmation of attendance to the program where I have been accepted.
My questions:

To anyone who has been part of these committees, why do universities withhold decisions this late? Is this a special case, or is this typical for graduate admissions?

How long should I wait before sending a confirmation of attendance? In other words, is there still some hope that one of my better choices might offer admission?


I do have until April 15th to decide but there is also the anxiety of waiting.
Edit: An important additional detail is that I am an international student currently in the US on a student visa (Master's) and I have to plan my travel (home country and back) and make visa arrangements etc. which also takes a significant amount of time.
You should delay your confirmation until the deadline. There's no reason not to. (Assuming the offer is valid until the deadline.) You may get a better offer.