Why can't you select an individual user when performing: FILTER > GO HERE TO MANAGE FILTERS > MANAGE FILTERS > YOUR FILTERS > SELECT A FILTER > SUBSCRIPTIONS > ADD SUBSCRIPTION > RECIPIENTS > cannot select individual user here - WHY?

BACKGROUND:
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Maybe I have missed something but I am having problems using subscriptions efficiently.
For some reason, when defining a "SUBSCRIPTION", you can only assign a "GROUP" to a "FILTER".

QUESTION No1:
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Why is it that you cannot assign an "INDIVIDUAL USER" to a "FILTER" when defining a "SUBSCRIPTION" ?
In other words, why can't you select an individual user when performing: FILTER > GO HERE TO MANAGE FILTERS > MANAGE FILTERS > YOUR FILTERS > SELECT A FILTER > SUBSCRIPTIONS > ADD SUBSCRIPTION > RECIPIENTS > cannot select an individual user at this point, only groups - WHY?

QUESTION No2:
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Can JIRA Support please provide their recommendation on how to assign an "INDIVIDUAL USER" to a "FILTER" when defining a "SUBSCRIPTION" ?

Thanks.