That would seem reasonable, SBF, 2-day conventions (only circuit and special day are called "assemblies" any more since the late 70's)
They keep "reminding" the rank and file about the poor Friday attendance and their being afraid to ask off from work. More likely, they only get one week vacation and don't want to "waste" it on a convention. Or worse yet get no paid vacation and have to eat the cost. Or they are scheduled during the school year and parents are reluctant to ask for time off for their children or the school system has stringent rules.
*** km 12/06 p. 3 par. 3 2007 "Follow the Christ!" District Convention of Jehovah’s Witnesses ***
Attend All Three Days: Jehovah provides an abundance of spiritual food for his people. (Isa. 25:6) This includes the spiritual banquet served at our annual conventions. It has been observed that the Friday attendance is considerably lower than that on other days. Make it your goal to enjoy all three of the refreshing convention days that Jehovah’s organization has prepared for us! If you need to request time off from your secular employment, make it a matter of prayer. Then ‘muster up boldness’ to talk with your employer as soon as the date of your convention is announced. (1 Thess. 2:2; Neh. 2:4, 5) It may prove helpful to explain to him that your annual convention is part of your worship. Doing this at an early date may make it easier for your employer to make adjustments so as to accommodate your request.
*** km 1/00 p. 1 pars. 2-5 Will You Be There? ***
2
Last year at some of the "God’s Prophetic Word" District Conventions, however, the attendance on Friday was substantially less than on Saturday and Sunday. This means that a large percentage of our brothers lost out on hearing convention parts that presented vital information about the prophetic word. They also forfeited delightful association with fellow believers.3
Do Not Let Secular Work Interfere: Concern about jeopardizing one’s employment may be the reason why some did not attend on Friday. However, many Witnesses have found that their employers are willing to cooperate with them in this matter if they ask for time off well in advance. One employer was so impressed by a pioneer sister’s firm determination to attend all congregation meetings and assemblies that he spent an entire day at her convention!
4
You should not assume that your employer is not disposed to grant you time off, nor should you conclude that missing a day of the convention will not matter. With heartfelt conviction, prepare to show your employer tactfully from the Scriptures why attending the convention is an important part of your worship. (Heb. 10:24, 25) Then put your full confidence in Jehovah’s promises, recognizing that whatever you require materially will be provided if you keep spiritual needs foremost in your life.—Matt. 6:33; Heb. 13:5, 6.5 The key factor is appreciation for "the more important things." (Phil. 1:10, 11; Ps. 27:4) This moves us to make plans to benefit fully from this vital provision from Jehovah. Start making your definite plans now, and be determined that you will be there all three days!
*** km 5/99 p. 2 Service Meetings for May ***25min: "1999 ‘God’s Prophetic Word’ District Conventions." (Paragraphs 1-16) Questions and answers. Read paragraphs 6, 8, 11, and 16. Stress reasons why we should attend the entire convention, including the Friday sessions. Emphasize the importance of following the Society’s direction to bring our own lunch to the convention each day.
*** km 12/99 p. 2 Service Meeting Schedule ***
Use the cited scriptures to show why all of us need to follow the Society’s direction closely. Stress the importance of everyone arranging definite vacation dates ahead of time in order to attend every day of the convention, including Friday. Commend the brothers for cooperating with the Society’s arrangements.
*** km 12/99 p. 4 par. 8 2000 "Doers of God’s Word" District Convention of Jehovah’s Witnesses ***
Satan tried to distract you from giving attention to spiritual things? Sadly, many brothers and sisters and their families are missing out on vital spiritual food. How? By not attending the Friday district convention sessions. In some instances it has been noted that a large percentage of our brothers are missing the spiritual instruction and fellowship that the Friday sessions provide.
Last four-day convention, perhaps 1993.
*** km 5/93 p. 3 par. 2 Benefit Fully From the 1993 "Divine Teaching" District Convention ***
A Four-Day Convention: The program will be presented at 156 convenient locations throughout the United States.