The lifting ain't that heavy. And besides, wouldn't you want your server spending its precious cycles on things the clients absolutely cannot handle?
You have two choices when taking an SPA approach:
1) Give your users a webpage that is usable, readable, and navigable as soon as they get it.
2) Give your users the skeleton of a webpage that they then have to accept the latency of javascript parsing and execution, and then the latency of data fetches.
we have the ability to do #1.
If you use the right technology, you can give a usable application out of the gate without waiting and use JSON data fetches for every subsequent request.
The reverse is also frequently true: if client rendering can improve cacheability or reduce the data going over the wire the radio savings will pay for a LOT of text updates. Similarly, if you can transfer a large listing without creating thousands of DOM nodes the results can be a wash depending on exactly how much data, the browser, etc.
There isn't a single right answer here - it really depends on the application and good analysis.