Why is the clearance delivery frequency included on an approach plate? Approach plates include frequencies in the order that pilots will require them, reading from left to right.

The example below from McClellan-Palomar’s ILS or localizer/DME approach to runway 24 is a fair representative. On the far right hand side just above the overhead view is the clearance delivery frequency of 134.85.

Talking to clearance delivery prior to departure is common, but when would a pilot talk to clearance delivery on arrival? What is the purpose of including this frequency on the approach plate?
The FAA Aeronautical Chart User’s Guide: Terminal Procedure Publications in section “Bottom Briefing Strip (Communications Information),” page 15 in the revision effective 29 March 2018, explains:

The communications briefing strip contains communication information when available, in separate boxes, listed from left to right in the order that they would be used during arrival …

Clearance Delivery (CLNC DEL) frequencies; where a Control Tower does not exist or is part-time, a remoted CLNC DEL may be listed …


Relevant to the briefing strip in the question, this section adds

Note: Part-time operations will be annotated with a star. Check Chart Supplement for times of operation.

According to the Chart Supplement for McClellan-Palomar, the tower is indeed part time.

AIRPORT REMARKS: Attended 1500–0600Z‡ …
COMMUNICATIONS: …
    TOWER 118.6 (1500–0600Z‡)

Other use cases when having the clearance delivery on the approach plate is convenient are obtaining a new clearance during a brief stop and closing an IFR flight plan through clearance delivery, either local or remote, when the tower is closed.