Its rather simple. Mandatory attendance. Just dont make the mandatoryness of it be 95% of events. Make it 60 or whatever floats your boat for the type of linkshell you want to create in regards to 'casualness'. Even in my LS that has a VERRY lax attendance policy, if you just stop showing up regularly, you will get 'demoted' to social status where you loose the ability to lot lewt until you get attendance back up. You post conflicts as they arise so the LS knows.
Just loosen the reigns. There is something between "90% attendence or DAS BOOT!" and some hippy world attendance where "its all good guy!".
Set an attendance. 80, 60, 75% whatever. Then a clause "if you drop below the determined attendance value, you get put on probation/no lotting/social status. When attendance is raised back to the determined amount, you may lot again".
You dont have to kick someone for dropping attendance. Just some level of probationary status till they get back. No need to polarize an LS into HARDCORE OR BUST! or SUPER SOCIAL LS!. Just make the edges less black and white.
There is also a rather interesting thing my LS does to curb skipping and showing up to lot stuff you want and manipulating the system that way. Most of the /lsmes are:
"to be determined" or
"Sat night: Voidwatch, Dynamis, Einherjar, Abyssea, or random zerg mobs"
No body in my LS ever friggin knows what hte next events are until sacs announce it at events. Kinda hard to 'skip' events you dont like and land the ones with your lewt when no one knows WTF event is ever going to be. Intentionally vague LS messages have actually helped curb event hopping.