People attack, they fail, they attack again. You know: just like they do in HOI if, for example, you try to defend France against a 1940 German invasion playing as the UK - stalemate warfare also occurs and its rather fun.
It's also necessary to point out that positional warfare both wasn't limited to WW1 (think of El Alamein, the ABC line, Monte Cassino, Kursk etc.) and wasn't the case on every front or every battle of WW1. By my count there were at least 10-12 campaigns in which large areas were over-run in fighting lasting weeks-months during WW1 (the Schlieffen plan, East Africa, Galicia, Poland 1915, Serbia 1916, Romania 1916, Mesopotamia, Palestine, Caporetto, Vittorio Venetto, the Baltic campaign, the Kaiserschlacht, the 100 days offensive etc.). Sure, the pace of combat in WW1 was slower than in WW2, but to call it static is to completely ignore every single example of it not being so.
HOI has to be able to simulate positional warfare well to simulate WW2 properly, so I really don't see the objection here.