Why Aren't Digital Scales Ever Accurate?

Hello everyone! I have been extremely busy lately and have gotten just a bit lax about hitting the gym daily. I recently started a new business in my town and have been doing lots of running around kicking it off. This shift of my attention means I take away focus on my exercise routine, so today I made a commitment to myself to get back on track. I started out by getting on the scale to do my weigh-in. At first I almost had a heart attack when the scale said 150! I thought, 'oh no! all my hard work to get the pounds off and they're creeping back on!'. (Remember, I started this journey to get fit in January and weighed in at about 157) I immediately jumped off and got back on. This time it said 146! My gosh, I lost 4 lbs in 5 seconds, amazing! I went for a third try and this time it said 147. I finally gave up, put my running shoes on and drove straight to the gym for a heavy calorie-burning workout. When I was done, I got on the scale they have there, you know, the old-fashion kind. It told me that I am 148.5. I'm still not satisfied, because at one point I had gotten down to 144. All this tells me is that I need to re-focus, get back on my daily work-out routine and continue to eat healthy, nourishing foods.... and that I need to toss out my old, digital scale!
Have a happy, healthy day and!