Because Muse keeps adding arming timers and nerfing heavy guns. Along with that and their inability to move well, just makes pilots shy away.
If a ship is going to be slow, then the guns need to offset that. It is taking a huge risk with lack of mobility and as such, needs a counter with being a ship you avoid at all cost because broadsides hurt. Old GOIO, this was how it was. Pilots learned fast to avoid their gun arcs and flew more evasive because one shot landing could often times ruin your day. Then people freaked out about 2hr artillery battles and next we had range cuts, velocity cuts, arming timers, power nerfs...list goes on.
When heavy guns were at their prime, there was nothing more satisfying than cramming a goldfish up someone's tailpipe and unloading both HF barrels. Ahh...good times.
Course if those get patched back, then Muse also has to patch the light ships back to being a bit more mobile to counter. So they've kinda dug themselves in a hole and Muse has already stated recently that they are happy with how the game is balanced right now. If you don't like it, let them know like I do. If they want to keep it as is, then fine, it is their game. But we need a hardcore mode or something which brings the power and speed back so people have an option. Course there are those that are afraid of that. Not that it wouldn't be a success but because it would. Afraid too many players will migrate to that and not play the original. But for that matter, if that is the case then it would be a clear sign where the design flaws are in GOIO.