Some noise modules will have S&H included (e.g. Doepfer A-118-2), but there are modules that provide S&H for arbitrary inputs (e.g. Joranalogue Select 2). Suppose you are generating pitch CV from an LFO or some complex combination of LFOs, maybe put through a quantizer. You want to hold the pitch for the duration of the envelope controlling amplitude. An S&H (triggered by the envelope's EOC output) can do that. The upcoming Joranalogue Step 8 is eight sample-and-hold circuits with various linking and control options. You can play a short sequence in by sampling at arbitrary points, and then play it back with a different rhythm entirely, and alter it on the fly.