Well, then ... why did you forget, when you (believe you've) actually cared?
There are many people in this thread who clearly do care and have trouble doing/remembering, so I'm not sure why you'd choose to respond this way to someone you're more likely to hurt.
Also, I see what you did there. :)
Most of the time, life pushes us towards the urgent & important, and even urgent & not-important. When you have a busy life (full time job building a side business with a family with kids), it's just very hard to put the non-urgent & important on the agenda.
Not all things that are important are urgent.
Just managing your own home requires a lot of organisation, and even if you do care, you will have a hard time to cope for long without some tools to help you (calendars, notes, schedules, only to name those). Unless someone does it for you. Or unless you live a very simple life that can fit in your head all the time, of course.
Likewise, seeing your friends fading away, not responding to you might be because they've just forgotten you, or don't want to see you anymore, or they are just drowning in their own life. And maybe with time they will cope/react differently, maybe not.
Considering that friendship/care only can be spontaneous and not prepared/provisional, this is disingenuous and borderline toxic (to both you and others).