New Views created in App Studio are linked to a Template to accommodate the now-Best-Practice configuration approach of a View being an ordered association Fields within a Region in the Template. This separates:
What data is shown (the View); from
How the data is laid out (the Template),
... and allows adjustments (including those delivered in Pega Upgrades) to the layout and styling of Views linked to the same Template to be implemented once (in the Template) and take effect over all Views linked to it with no further refactoring.
As of Pega 8.2, new Section rules created in Dev Studio are Design Templates by default to encourage this pattern as the new Pega Best Practice.
Unlinking a View from a Template is to require that the View encapsulates both its data and layout implementation in the same rule. This yields a maintenance overhead - usually felt at Upgrade-time - if similar layout patterns are implemented across many Sections (even if their styling is sourced from the same Skin).
A View cannot be configured in App Studio if it is not linked to a Template. A View originally authored in Dev Studio can still be configured in App Studio so long as it is linked to a Template.