Why do long ChatGPT chats slowly become unusable?

I’ve been using ChatGPT a lot for work lately, and something has been bothering me. At the beginning, everything feels smooth. Fast replies, easy scrolling, no friction. But once a conversation gets long enough… it starts falling apart. Replies take longer. Scrolling feels laggy. Finding something you said earlier becomes weirdly hard. And the worst part is - this usually happens in the exact situations where you need long context. Debugging, writing, refining ideas… you can’t just start a new chat every time.