Due to the altcoin, Bitcoin still has not been able to get a full rise, because those new altcoins are drawing money from Bitcoin!
I think that's not the reason bitcoin hasn't increased because new altcoin has been born continuously since last year. If bitcoin was affected, it wouldn't set a record in December last year.
People are always bound to look for silly reasons as to why the bitcoin market is down. First and foremost, the whole market is down and altcoin in general have been far beaten to the ground with bitcoin gaining dominance by the day, which makes me wonder if some just do not like getting themselves aware of the things going on or they just simply prefer staying in a limbo.
A lot of traders and investors are actually looking forward to this period as it is and I will not be surprised looking at the way the market has been trying to gear up for days now. September could bring about some bullish movement, no one knows, but for me, I know in a good condition of btc holding strong, the altcoins will tend to do very well and that won't still stop bitcoin in anyway.
Although, with the way bitcoin is, there is a lot of uncertainty in the market to which direction bitcoin is going to be taking and that simply is affecting participation in alts as much as a lot of them wants to move and showing some good sign lately. As the coming weeks pan out, will determine if there would be anything serious at all before this month ends.