Why are there some airports not charted as service-available when FBO provides fuel?
The chart supplement states that 1O5 is unattended, which fails the attendance requirement. And fuel is self-service for both 1O5 (FBO: Steelman Aviation) and SIY (FBO: Eagles Nest Aviation), which is also a reason for not having the tick marks.
Tick, tock
Your concern was discussed in the Charting Group Meeting 15-01 on April 28-30, 2015 (exactly two years ago):

Many pilots believe that the tick marks indicate the airport has fuel.
Over the past 20 years, many airports have gone to self-service fueling, eliminating the need for an &quot;attendant&quot; to be on duty to provide fuel services.
Several airports have contacted us, requesting the tick marks be placed on their airport symbol because they have fuel.
Recommendations:
Revise the charting criteria to:
Services available – To qualify as an airport with &quot;services available&quot;, the minimum requirement that fuel is readily available (self-service or via attendant) 24 hrs/day.
Eliminate the requirement for attendant hours.

Outcome:

Rich Fecht, AJV-5223, reviewed the topic. Rich stated that the IACC Requirement Document has been signed and is ready to implement. Visual Charting is parsing through the data to get a list of airports that meet the fuel availability requirements and will soon start updating the VFR charts. Rich anticipates that the updated airport fueling information to be reflected on all charts within about two years. This change will affect public airports only.
Lynette Jamison, AJR-B11, stated that the proponent of this item should reach out to the state inspectors to let airports know how they can get fuel availability shown at their airport.

That means that both airports should get their tick marks soon enough if they want to.
2018 Update
With the release of new sectional charts on 29 Mar 2018, SIY got the tick marks:


(skyvector.com)

2021 Update
Both now have the tick marks:




Note: the chart supplement does not have to mention temporary shortages according to IACC 8 section 3.1.5.5.4.5:

The following type data shall NOT be published in the SERVICES and REMARKS sections:

g. Temporary shortages of certain types of fuel, starting equipment, or other aircraft services;