Expounding on "opt-in for performance reasons"

In the documentation for both Tooltips and Popovers is the caveat: “opt-in for performance reasons, so you must initialize them yourself.” But I’m having trouble finding a detailed explanation of “performance reasons.” The caveat is at least 6 years old, which makes me wonder if it’s still true.

Also, many people miss this caveat when reading the documentation, for example #24985 and #15458. So it would be great if Tooltips and Popovers could actually be automatically initialized in a performant way. That might also pair nicely with using MutationObserver to automatically remove Tooltips in v5.

[lacutah]

Follow up / tangential to this as a user of bootstrap:

1. The “opt-in” requirement and guidance already seemed weird because adding the `data-[bs-]toggle='tooltip`` attribute to an element already is EXPLICIT that you want tool-tip popup behavior.
2. Inconsistency with other controls - why the additional extra step of manual JavaScript initialization when default behavior it to self-initialize from data attributes.

[mdo]

I agree with @XhmikosR on needing to re-evaluate this. @twbs/js-review Can any of you review and make a suggestion for how to better handle tooltips and popovers here without requiring extra work?