IMO it's general usability. For example a very common thing you might want to do is add text (or any other layer) on top of an image and then center that text

IMO it's general usability. For example a very common thing you might want to do is add text (or any other layer) on top of an image and then center that text / layer either vertically or horizontally relative to the image. In Photopea you create a text layer and then drag it near the middle and it'll show you guidelines when you're close and then snap into the perfect center (either vertically, horizontally or both). It takes like 2 seconds and feels intuitive. In GIMP you have to make sure you switch to the alignment tool which is hidden by default so you need to remember to hit Q to activate it or hover over the move tool and select it but if you hit Q you better make sure you're not in any text input because it'll insert "Q" instead of switching your tool, but since you're adding text chances are you will be so you need to remember to click away. Then you need make sure you click an active area of your text layer and click the align horizontal icon, then you need to click the align vertical icon. Then if you decide you want to change your text you have to repeat this whole process again. Another example is adding a simple stroke (line) around some text or other layer effects that Photoshop has had for over 10+ years. In Photopea, you open up layer styles, pick the stroke option and can tweak the colors and thickness very quickly. After applying the style you can change and move around your text and the styles are applied to it automatically, it feels intuitive to use. In GIMP I spent an hour researching plugins to add this behavior and after picking one it technically works but the user experience is pretty hostile. It creates the stroke as a separate layer so you can't move your text and the stroke together unless you remember to link them, and if you decide to change your text content or size you have to delete the old stroke layer and make a new one. GIMP is really good in terms of what it can do but using it feels like death by a thousand paper cuts because you need to do so many steps to accomplish what feels like basic things that other editors have had for years when it comes to user friendly features. I understand creating a highly polished image editor isn't easy and honestly if I knew their code base I would open a PR for the snap to center guidelines but at this point I have to imagine if they wanted to add that feature it would have been added. From the outside it feels like it hasn't been added because they don't want that feature, but as an end user that makes me wonder why. It's such a useful thing.