Why is the .tcx from BC so minimized?

When I upload a track from my Forerunner 610 GPS watch into Basecamp and I then export the same file to another .tcx file, the exported file is way smaller then the original data. All kind of information is lost.

Part of he input file from the GPS watch:

<Trackpoint>
<Time>2013-09-11T17:15:28Z</Time>
<Position>
<LatitudeDegrees>51.8493667</LatitudeDegrees>
<LongitudeDegrees>5.8682784</LongitudeDegrees>
</Position>
<AltitudeMeters>11.3999996</AltitudeMeters>
<DistanceMeters>2.5799999</DistanceMeters>
<HeartRateBpm xsi:type="HeartRateInBeatsPerMinute_t">
<Value>113</Value>
</HeartRateBpm>
<Extensions>
<TPX xmlns="www.garmin.com/.../v2" CadenceSensor="Footpod">
<Speed>1.5390000</Speed>
</TPX>
</Extensions>
</Trackpoint>


And at every 1000m point there is additional information:

<Trackpoint>
<Time>2013-09-11T17:20:07Z</Time>
<Position>
<LatitudeDegrees>51.8488438</LatitudeDegrees>
<LongitudeDegrees>5.8560486</LongitudeDegrees>
</Position>
<AltitudeMeters>28.3999996</AltitudeMeters>
<DistanceMeters>1000.7399902</DistanceMeters>
<HeartRateBpm xsi:type="HeartRateInBeatsPerMinute_t">
<Value>172</Value>
</HeartRateBpm>
<Extensions>
<TPX xmlns="www.garmin.com/.../v2" CadenceSensor="Footpod">
<Speed>3.6500001</Speed>
</TPX>
</Extensions>
</Trackpoint>

</Track>
<Extensions>
<FatCalories xmlns="www.garmin.com/.../v1">
<Value>0</Value>
</FatCalories>
<LX xmlns="www.garmin.com/.../v2">
<AvgSpeed>3.5820000</AvgSpeed>
</LX>
</Extensions>

</Lap>



And then the next 1 km lap begins:
<Lap StartTime="2013-09-11T17:20:07Z"> .....


The exported file from BC for the same point however is:

<Track><Trackpoint>
<Time>2013-09-11T17:15:28Z</Time>
<Position><LatitudeDegrees>51.849366724491119</LatitudeDegrees><LongitudeDegrees>5.868278369307518</LongitudeDegrees></Position>
<AltitudeMeters>11.399999599999999</AltitudeMeters>
<HeartRateBpm><Value>113</Value></HeartRateBpm>
</Trackpoint>


But there is no data anymore on distance and the whole track is also not divided in km-parts.

Why is all this essential information deleted at export? (Or maybe already at reading the input file.)