The very same can be said about India in that India does not have COMPLETE control over the glacier either. Given the Pakistani positions, Indians cannot allow mountaineering expeditions onto the glacier. So while dominating the heights at the glacier is advantages tactically in that its hard to displace built up positions when you have to go up and fight, the reality is that neither country can realistically use the real estate for their purpose.
Like the LoC, Siachen is also frozen in the status-quo with both sides contesting.
So while you sit at the higher elevations, you also have more logistical challenges with supplying and dumping at the positions. We are occupying positions that prevent the glacier from being visited by tourists etc. The net benefit is none for either but it is also something that Pakistan won't give up on for as long as the Indians are there. The land is ours, and we are going to stay on it for as long as it takes for both sides to mutually demilitarize.