Because it looks really cool and it could bring in Star Wars fans as tourists since Ireland could have the biggest lightsaber in the world! People will be coming home to see this pretty cool thing that the spire has turned in to a really cool monument. Think of it as a shining beacon to request their home coming, a bit like a bat sigil for Irish heroes.
Also, no one likes the spire and people have been taking the mick out of it since its been put up, but everyone likes Star Wars so its a win/win situation!
So the advantages for the country would be:

• More money will be brought in because of tourism 
• People wont hate the Spire anymore and make fun of it
• It wont be an eyesore anymore
• economic growth
• People will be coming home to see this epicness

If you agree with me and think we should keep it like this for a good long while anyway, then please sign and forward it to your friends, family and Dublin City Council! 
Thank you very much for your time to read this it was much appreciated.

Update: I've decided to add some of the comments our supporters have been posting. If anyone has a problem with theirs being seen, please message the Facebook page and we'll take it down no problem

• The spire is a very unique monument, however it fails to please the eye at night.Dublin needs to light up more beautiful buildings and monuments at night, the spire is at the centre of dublin and should dazzle locals and tourists at night, which before it was lit up it failed to do.
  Shane , Dublin/Galway
• 
  I think it makes the spire look so much cooler and it is the best thing ever to have been made in this country
  Conor, Dublin
  
  

• I'm signing because I love Star Wars and this is genuinely a good idea for the country, there will be a movie every year until at least 2019 anyway so it will continue to be relevant

  Dan, Dublin
  
  

• Not only does the Spires new look promote Nerd Culture but it certainly would also serve as a great tourist attraction in our beautiful city. To look into our skyline and see the glowing blue light on an otherwise pointless(no pun intended) landmark gives purpose to it. I love my city and I love this new addition so please keep it for the world to see. May the force be with you all.
  
  Stephen, Dublin
  
  
• It's clear The spire is not liked by most Irish people. Most see it as a waste of money at this stage but since it was turned into a light saber it has been going around social media like wild fire. This is great, and will help tourism so much. Please keep the spire looking this way
  
  Simon , Dublin
  
  
• It makes the spire stand out more better from a tourist point of view
  
  Niall, Dublin
  
  

• It looks far better now than ever before

  James, Dublin