Place a call from the record and it is attached to it. An inbound call finds the lead it belongs to. The recording and the transcript live on the same record, so the next person to pick it up has the conversation, not a summary of it.
Telephony bolted on is telephony you reconcile. A separate dialler means a call log you match against leads by phone number, badly.
Searchable, replayable, and attached without anybody logging it.