If people trade STEEM for BTC and they see BTC go up in value but decide not to sell STEEM, that is the equivalent of accepting that their STEEM has also increased in value. Example:
Say I use 5 USD to buy BTC to use to buy STEEM with, because I think 1 STEEM is worth 5 USD. Let's say I want to sell that 1 STEEM once it's USD equivalent value goes to 6 USD. That means that if BTC goes up 20%, I should now sell my STEEM for BTC and convert that to USD. IF I DON'T do that, then i must think that the value of 1 STEEM has now INCREASED to 6 USD. Hence if the value of BTC goes up in USD terms but the BTC equivalent of STEEM stays the same, one has to assume that the value of STEEM has also increased.
This is the reason why Tradeviewer converts alts into USD equivalents whenever possible.
What you are saying still make no Sense, and reality dont bend to fit what you want.
You are still buying steem with BTC. So the steem/usd still derive from BTC/usd pair.
You cant accurately evaluate the usd price of something If this something is not directly traded for usd.
Any price movements that happen on steem/usd is heavily affected by the price of BTC/usd.
The price increase because the BTC price increased. Check the graph below from Tradingview that show the % price change from these 3 pair:
https://steemit-production-imageproxy-thumbnail.s3.amazonaws.com/U5dtgHARsAjv83vFzsbMMrN1Jrqeciw_1680x8400
Since It started Trading on bittrex, steem Lost 64% of its price, while Bitcoin increased 2300% of the price.
Now Tell me, what made the steem/usd price rise? If you didnt Saw It yet i Will Tell you: BTC is what drive steem/usd price up.
All movements of steem/usd price ia a reflectir of BTC/usd graph.