Having worked on presentation software, it's more complicated than what it looks like in its surface.
First, considering the base/generic case, you can't really beat Powerpoint, Keynote and Google Slides, they are somewhat free/included in basic accounts, they will get the job done, people are used to Powerpoint, and it's not the core product of any of these companies, there's very little incentive for them to improve that.
Second, because you can't compete on base case, a company needs to target those who will willingly pay for presentation software, that's sales and marketing, they don't care about beautiful software, they care about conversion and data.
And lastly, most presentations are bland, the more you invest in a great creation and editing experience, the more complicated it gets and makes it less likely that people who just want to create basic presentations actually do it, doesn't matter if you have tutorials or templates, they will make crappy presentations to get the job done, if they try to do add a little touch to it they will likely overuse animations or similar features and make it even crappier.
In the end there are very few people who put effort into creating actual presentation decks, the actual content being presented is far more important or a presentation is often a hurdle to get over with, such as doing internal presentations or presenting your school assignments.
Even in conferences you still get really bad presentations, the better ones are mostly remembered not because of the quality of the slides, but the contents and the skills of the presenter.
First, considering the base/generic case, you can't really beat Powerpoint, Keynote and Google Slides, they are somewhat free/included in basic accounts, they will get the job done, people are used to Powerpoint, and it's not the core product of any of these companies, there's very little incentive for them to improve that.
Second, because you can't compete on base case, a company needs to target those who will willingly pay for presentation software, that's sales and marketing, they don't care about beautiful software, they care about conversion and data.
And lastly, most presentations are bland, the more you invest in a great creation and editing experience, the more complicated it gets and makes it less likely that people who just want to create basic presentations actually do it, doesn't matter if you have tutorials or templates, they will make crappy presentations to get the job done, if they try to do add a little touch to it they will likely overuse animations or similar features and make it even crappier.
In the end there are very few people who put effort into creating actual presentation decks, the actual content being presented is far more important or a presentation is often a hurdle to get over with, such as doing internal presentations or presenting your school assignments.
Even in conferences you still get really bad presentations, the better ones are mostly remembered not because of the quality of the slides, but the contents and the skills of the presenter.