As well they should. This one poll gives the appearance of a trend towards Yes and a dramatic close finish, but Yes have always been behind by a fairly consistent margin [0]. Just so happens the odd poll (~2/50 now) finds a Yes majority by crook or by hook (e.g. SNP commission a poll) and it makes a nice news piece. I did a quick analysis of that polling data should anyone be interested [1].
[0] http://ukpollingreport.co.uk/scottish-independence-referendu...