@Demosthenes That’s a good question, and of course the situation varies by place and especially by when in the past you mean. Certainly there have always been men repressing anger and/or lashing out in violence. The frequent gun killing sprees seem relatively new.
I think I’d have to give it a lot more thought, and/or find some sources that have already given such questions serious study. And I’m tired, but to offer a couple of first-stabs at it:
The main negative differences that come to my mind that I notice over the last few decades in the USA is what seems to me the reduced acceptance for unsupervised outdoor roaming and physical antics by boys, as well as more control and monitoring and restriction/reaction by school authorities, cameras everywhere and cell phones making kids always available by phone. Also what seems to me like a sharp decline in adult male role modeling and a general lack of sane adult behavior in the culture, what with the news media devolving into corporate mouthpieces and so many elected politicians not even seeming to try to be intelligent or honest, and all the other stress/chaos stories going around (including the mass shootings, often at schools).
I also think that the increased control by parents and communities and authorities, though it may have the intention to make things safer, tends to create a stifling feeling of powerlessness and suspicion and resentment and so on. Violent rampages tend to be a reaction to having been made to feel powerless and unheard.
On the other hand, there have been some great positive changes. In some ways there are more and new types of outlets and counsel available. But the usual social situation for most men in our society is still pretty bleak in terms of having people they feel they can open up to, or even having much self-awareness that anything like that is something they might want to do. That situation was probably much more stifling in the 1950’s, so why no rash of shooting sprees? I don’t know, but I imagine mainly differences in the thinking back then. I think @Soubresaut is probably right that it has become a thing that people now think of to do because it is in the common thinking now, while random shooting sprees were not so much “a thing” anyone might consider, in the past. There have been decades of exposure and normalization of the idea now.