Packages and memberships remove a decision from every visit and smooth income for a practice with fixed capacity. They work best when simple enough to explain in one sentence, since complicated tier structures rarely get purchased.
Both work, and both solve the same problem: a practice with fixed capacity and variable demand.
What they do:
Two design rules. Keep it simple enough to explain in one sentence. Complicated tier structures do not get bought, and they create administrative work a solo practitioner does not have time for. And decide your expiry and transfer policy in advance, since unused sessions are the most common source of awkward conversations.
Memberships suit practices with a stable regular clientele. Packages suit practices with more variable attendance. Many therapists start with a simple package of a few sessions at a modest saving and add a membership later if demand supports it.