Yes, Bitcoin is kind of a Store of value but since the value of STEEM or other cryptocurrencies are pegged in Satoshis so when Bitcoin rises it tends to bring the rest of the Cryptos up with them.
For example the Price of BTC is 10 USD and STEEM is 1 USD but it is pegged at 0.1 BTC.
If BTC price goes to 50 USD in a Bull run than it will lead STEEM price to about 5 USD since STEEM is around 0.1 BTC later it might consolidate and go a bit low and settle say about 2 USD but the fact remains that STEEM increased with the sudden rise of Bitcoin.
That' my thought.