When we think about basicity, those species which have more electronegative terminal atoms do not have a higher level of basicity than those with less electronegative ones. This is because electronegative terminal atoms attract electrons.
We already know bases as electron pair donors but in the case of electro negativity of terminal atoms and their behavior with electrons, what can we develop as a reason of lower basicity? The reverse situation is correct for acidic compounds.
Additionally, if alkyl groups are terminal atom attached to the center atom we have point that explains the situation like this; The more carbon atoms, the lower electro negativity but this does not effect the center atom because of their larger size due to more carbon atoms. Steric effect is starting here because larger sizes hold the electrons with smaller angle of center atom - terminal atom. In acidic molecules we have obviously larger bond angle like 120 degree in boron triflouride. So, can we argue that such angle makes acids exceptions when talking about steric effect ?
The question is why more electronegative terminal atoms containing bases weaker. Additionally if the size of terminals are larger then this rules out that effect in bases because larger sizes hold electrons attracting them so if you have larger size in terminal atoms your base is again weaker but this is not correct for acids because of larger angles. Can every acid molecules be considered like this ?