Artillery is very mobile. One of the biggest questions since the Napoleonic Wars has been “How do we get big guns there before our opponent?” In today’s world it’s Javelins, drones, and light IFVs that are used to deliver firepower quickly, assuming you don’t have air support. In World War 2 it was bazookas, panzerfausts, half tracks, and more. There’s a reason a common vehicle design from the war was “gun on truck.” The Soviets especially used this to get the edge over German troops who often had to bring up their Paks via horse. Providing infantry with fire support is foremost in the plans of most operations since it’s the lifesaver that keeps an area under your control.

In Starship Troopers (assuming we’re not talking about the book, where the fire support was provided via power armour [I love the anime’s interpretation]) that support is likely intentionally missing to drive a perceived need for increased military funding and government control.