Because people often don’t look at their own behavior. Or, they say stupid things and don’t know how it makes the other person feel.
Do they actually complain? Or, are they just saying things like, “I haven’t heard from you in so long,” and you take that as, “why haven’t you called, you aren’t a good friend?”
I suggest next time someone says something along the lines you are talking about say right back, “I haven’t heard from you either,” or “I could say the same to you.” there might be a little risk it pisses them off, you know better how they might react. You also know if you are willing to take the risk.
My husband used to call his parents or his dad would call us on most Sundays. Once in a while he woulld call a different day of the week, and if his mom answered she would answer, “Oh what a miracle,” and it really bothered my husband, like he is the bad son. She never called us. So, he told her one day how much saying it was a miracle he called bothered him. Nothing much came of it, I don’t think she really understood. Then there was another incidient where my husband and I were accused of not doing enough for the family, which if I told you the reality you would call her ungrateful, but I won’t tell the whole story. One day, when something came up about phine calls again I asked her, “is it some cultural thing where the children are supposed to call the parent, the responsibility is on us?” if that was the case I was fine playing along with it, but her answer was, “no.” About two years later she admitted or had some sort of epiphany that she doesn’t call and took some responsibility. I don’t mean we didn’t see her for two years, I just mean the topic came up again and she said it without provocation.
I have no idea what the real situation is with your friends or you. Maybe they called last time and were waiting for you to call, and when you didn’t they took that as you didn’t want to be in contact. It can easily all be a big misunderstanding.
My advice is when people do call you, always be happy to hear from them. You get what you give. I’m not assuming you don’t do that.
Give it two or three tries, you call them, and then see if they reciprocate. Or, at minimum if they are happy to hear from you and you talk talk talk. If not, I guess they suck as friends. Or, they have young children.