Sure there are better ways to do it, but for less tech savy users a combination of browser windows and tabs are a good way to keep track of "thought branches". I do it sometimes, I google a topic (and open tabs) then when an interesting branch comes up I spawn a new browser window and then repeat the process again.
Why should lots of open tabs cause a problem? Worse case a browser should just unload them and pull them back from the cache when they are activated.
When pages were (mostly) static you could have 100 tabs on a slow machine and it wouldn't matter because they were mostly in the swap file. The more pages try and become active without a mechanism for the browser to "pause" them the bigger the problem lots of tabs becomes.