Some people will also sell bitcoin at anytime.
But you are right that those altcoins are shit coin. My personal message is true about altcoins because they are truly shit coins.
XRP all time high was on January 4, 2018 which was $3.84. XRP has not yet gotten to all time high, do not believe all those fake news like when it got to $.3.3 in January that many people are saying it got to all time high, it is a lie.
Bitcoin is a store of value while altcoins are for pump and dump.
Definitely agree with you about people also going to take profit sooner or later with bitcoin but the difference with all this shitcoins is one thing which is if a bitcoin investor actually takes profit from bitcoin there is high probability of the investor actually buying back again later or he is simply just selling little portions of his holdings and will most definitely be holding his current position but for Altcoins it is not the same, the scare is that this is most probably an exit from the market. Bitcoin is the only coin that people treat as a store of value and hodl Altcoins are simply treated as pump and dump tokens, and it is the major reason I still Stand on that Altcoins are pure gamble and not a diversification means.
For the price of XRP reaching all time high I think the discrepancy was from the major aggregators we have, for example Coingecko had on their platform that the price got a new all time high when it got to $3.65 on July 18th while CoinMarketCap still has the all time high has $3.84 which was set in January 4, 2018. So most people might be confused and go with the coingecko price